diff --git a/acceptance-tests/src/test/java/tech/pegasys/pantheon/tests/acceptance/dsl/node/ThreadPantheonNodeRunner.java b/acceptance-tests/src/test/java/tech/pegasys/pantheon/tests/acceptance/dsl/node/ThreadPantheonNodeRunner.java
index 8bb574c720..0f36207bae 100644
--- a/acceptance-tests/src/test/java/tech/pegasys/pantheon/tests/acceptance/dsl/node/ThreadPantheonNodeRunner.java
+++ b/acceptance-tests/src/test/java/tech/pegasys/pantheon/tests/acceptance/dsl/node/ThreadPantheonNodeRunner.java
@@ -137,7 +137,8 @@ public void startNode(final PantheonNode node) {
         PantheonEvents.class,
         new PantheonEventsImpl(
             pantheonController.getProtocolManager().getBlockBroadcaster(),
-            pantheonController.getTransactionPool()));
+            pantheonController.getTransactionPool(),
+            pantheonController.getSyncState()));
     pantheonPluginContext.startPlugins();
 
     final Runner runner =
diff --git a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/SyncStatus.java b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/SyncStatus.java
index 165df0e95d..72596546b1 100644
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/SyncStatus.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/SyncStatus.java
@@ -14,7 +14,7 @@
 
 import java.util.Objects;
 
-public final class SyncStatus {
+public final class SyncStatus implements tech.pegasys.pantheon.plugin.data.SyncStatus {
 
   private final long startingBlock;
   private final long currentBlock;
@@ -26,18 +26,22 @@ public SyncStatus(final long startingBlock, final long currentBlock, final long
     this.highestBlock = highestBlock;
   }
 
+  @Override
   public long getStartingBlock() {
     return startingBlock;
   }
 
+  @Override
   public long getCurrentBlock() {
     return currentBlock;
   }
 
+  @Override
   public long getHighestBlock() {
     return highestBlock;
   }
 
+  @Override
   public boolean inSync() {
     return currentBlock == highestBlock;
   }
diff --git a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/Synchronizer.java b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/Synchronizer.java
index 408674be8b..eb2ed49400 100644
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/Synchronizer.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/Synchronizer.java
@@ -12,6 +12,9 @@
  */
 package tech.pegasys.pantheon.ethereum.core;
 
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
+import tech.pegasys.pantheon.plugin.services.PantheonEvents;
+
 import java.util.Optional;
 
 /** Provides an interface to block synchronization processes. */
@@ -27,12 +30,7 @@ public interface Synchronizer {
    */
   Optional<SyncStatus> getSyncStatus();
 
-  long observeSyncStatus(final SyncStatusListener listener);
+  long observeSyncStatus(final PantheonEvents.SyncStatusListener listener);
 
   boolean removeObserver(long observerId);
-
-  @FunctionalInterface
-  interface SyncStatusListener {
-    void onSyncStatus(final SyncStatus status);
-  }
 }
diff --git a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/DefaultSynchronizer.java b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/DefaultSynchronizer.java
index 528705a4fa..20993cd01c 100644
--- a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/DefaultSynchronizer.java
+++ b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/DefaultSynchronizer.java
@@ -15,7 +15,6 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import tech.pegasys.pantheon.ethereum.ProtocolContext;
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthContext;
 import tech.pegasys.pantheon.ethereum.eth.sync.fastsync.FastDownloaderFactory;
@@ -29,7 +28,9 @@
 import tech.pegasys.pantheon.ethereum.worldstate.Pruner;
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStateStorage;
 import tech.pegasys.pantheon.metrics.PantheonMetricCategory;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 import tech.pegasys.pantheon.plugin.services.MetricsSystem;
+import tech.pegasys.pantheon.plugin.services.PantheonEvents.SyncStatusListener;
 import tech.pegasys.pantheon.util.ExceptionUtils;
 import tech.pegasys.pantheon.util.Subscribers;
 
@@ -176,10 +177,11 @@ public Optional<SyncStatus> getSyncStatus() {
     if (!running.get()) {
       return Optional.empty();
     }
-    if (syncState.syncStatus().getCurrentBlock() == syncState.syncStatus().getHighestBlock()) {
+    final SyncStatus syncStatus = syncState.syncStatus();
+    if (syncStatus.inSync()) {
       return Optional.empty();
     }
-    return Optional.of(syncState.syncStatus());
+    return Optional.of(syncStatus);
   }
 
   @Override
@@ -194,6 +196,6 @@ public boolean removeObserver(final long observerId) {
   }
 
   private void syncStatusCallback(final SyncStatus status) {
-    syncStatusListeners.forEach(c -> c.onSyncStatus(status));
+    syncStatusListeners.forEach(c -> c.onSyncStatusChanged(status));
   }
 }
diff --git a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncState.java b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncState.java
index 257a83803c..c3cbc57546 100644
--- a/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncState.java
+++ b/ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncState.java
@@ -16,14 +16,16 @@
 import tech.pegasys.pantheon.ethereum.chain.ChainHead;
 import tech.pegasys.pantheon.ethereum.core.BlockHeader;
 import tech.pegasys.pantheon.ethereum.core.SyncStatus;
-import tech.pegasys.pantheon.ethereum.core.Synchronizer.SyncStatusListener;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthPeer;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthPeers;
 import tech.pegasys.pantheon.ethereum.p2p.rlpx.wire.messages.DisconnectMessage.DisconnectReason;
+import tech.pegasys.pantheon.plugin.services.PantheonEvents.SyncStatusListener;
 import tech.pegasys.pantheon.util.Subscribers;
 
 import java.util.Optional;
 
+import com.google.common.annotations.VisibleForTesting;
+
 public class SyncState {
   private static final long SYNC_TOLERANCE = 5;
   private final Blockchain blockchain;
@@ -49,17 +51,22 @@ public SyncState(final Blockchain blockchain, final EthPeers ethPeers) {
         });
   }
 
-  private void publishSyncStatus() {
+  @VisibleForTesting
+  public void publishSyncStatus() {
     final SyncStatus syncStatus = syncStatus();
-    syncStatusListeners.forEach(c -> c.onSyncStatus(syncStatus));
+    syncStatusListeners.forEach(c -> c.onSyncStatusChanged(syncStatus));
   }
 
   public void addInSyncListener(final InSyncListener observer) {
     inSyncListeners.subscribe(observer);
   }
 
-  public void addSyncStatusListener(final SyncStatusListener observer) {
-    syncStatusListeners.subscribe(observer);
+  public long addSyncStatusListener(final SyncStatusListener observer) {
+    return syncStatusListeners.subscribe(observer);
+  }
+
+  public void removeSyncStatusListener(final long listenerId) {
+    syncStatusListeners.unsubscribe(listenerId);
   }
 
   public SyncStatus syncStatus() {
@@ -141,10 +148,10 @@ public long bestChainHeight(final long localChainHeight) {
   }
 
   private synchronized void checkInSync() {
-    final boolean currentSyncStatus = isInSync();
-    if (lastInSync != currentSyncStatus) {
-      lastInSync = currentSyncStatus;
-      inSyncListeners.forEach(c -> c.onSyncStatusChanged(currentSyncStatus));
+    final boolean currentInSync = isInSync();
+    if (lastInSync != currentInSync) {
+      lastInSync = currentInSync;
+      inSyncListeners.forEach(c -> c.onSyncStatusChanged(currentInSync));
     }
   }
 
diff --git a/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncStateTest.java b/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncStateTest.java
index f5caa86a94..06d5f7711e 100644
--- a/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncStateTest.java
+++ b/ethereum/eth/src/test/java/tech/pegasys/pantheon/ethereum/eth/sync/state/SyncStateTest.java
@@ -31,10 +31,10 @@
 import tech.pegasys.pantheon.ethereum.core.BlockHeader;
 import tech.pegasys.pantheon.ethereum.core.BlockHeaderTestFixture;
 import tech.pegasys.pantheon.ethereum.core.Hash;
-import tech.pegasys.pantheon.ethereum.core.Synchronizer.SyncStatusListener;
 import tech.pegasys.pantheon.ethereum.eth.manager.ChainState;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthPeer;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthPeers;
+import tech.pegasys.pantheon.plugin.services.PantheonEvents.SyncStatusListener;
 import tech.pegasys.pantheon.util.uint.UInt256;
 
 import java.util.Collections;
@@ -237,7 +237,7 @@ public void shouldSendSyncStatusWhenBlockIsAddedToTheChain() {
                 new BlockBody(Collections.emptyList(), Collections.emptyList()))),
         blockchain);
 
-    verify(syncStatusListener).onSyncStatus(eq(syncState.syncStatus()));
+    verify(syncStatusListener).onSyncStatusChanged(eq(syncState.syncStatus()));
   }
 
   private void setupOutOfSyncState() {
diff --git a/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/GraphQLDataFetchers.java b/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/GraphQLDataFetchers.java
index f85953ec35..f5bdae7ded 100644
--- a/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/GraphQLDataFetchers.java
+++ b/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/GraphQLDataFetchers.java
@@ -18,7 +18,6 @@
 import tech.pegasys.pantheon.ethereum.core.Account;
 import tech.pegasys.pantheon.ethereum.core.Address;
 import tech.pegasys.pantheon.ethereum.core.Hash;
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.core.Transaction;
 import tech.pegasys.pantheon.ethereum.core.WorldState;
@@ -38,6 +37,7 @@
 import tech.pegasys.pantheon.ethereum.p2p.rlpx.wire.Capability;
 import tech.pegasys.pantheon.ethereum.rlp.RLP;
 import tech.pegasys.pantheon.ethereum.rlp.RLPException;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 import tech.pegasys.pantheon.util.bytes.Bytes32;
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 import tech.pegasys.pantheon.util.uint.UInt256;
diff --git a/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/internal/pojoadapter/SyncStateAdapter.java b/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/internal/pojoadapter/SyncStateAdapter.java
index 9aa1505d13..97d7df27b7 100644
--- a/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/internal/pojoadapter/SyncStateAdapter.java
+++ b/ethereum/graphql/src/main/java/tech/pegasys/pantheon/ethereum/graphql/internal/pojoadapter/SyncStateAdapter.java
@@ -12,7 +12,7 @@
  */
 package tech.pegasys.pantheon.ethereum.graphql.internal.pojoadapter;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 
 import java.util.Optional;
 
diff --git a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheck.java b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheck.java
index 70645f0875..d623d6390f 100644
--- a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheck.java
+++ b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheck.java
@@ -12,11 +12,11 @@
  */
 package tech.pegasys.pantheon.ethereum.jsonrpc.health;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.jsonrpc.health.HealthService.HealthCheck;
 import tech.pegasys.pantheon.ethereum.jsonrpc.health.HealthService.ParamSource;
 import tech.pegasys.pantheon.ethereum.p2p.network.P2PNetwork;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
diff --git a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/results/SyncingResult.java b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/results/SyncingResult.java
index 7887d527c8..35ead9a3da 100644
--- a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/results/SyncingResult.java
+++ b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/results/SyncingResult.java
@@ -12,7 +12,7 @@
  */
 package tech.pegasys.pantheon.ethereum.jsonrpc.internal.results;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 
 import java.util.Objects;
 
diff --git a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java
index 4225f15deb..2298420283 100644
--- a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java
+++ b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/SubscriptionManager.java
@@ -37,7 +37,7 @@
 
 /**
  * The SubscriptionManager is responsible for managing subscriptions and sending messages to the
- * clients that have an active subscription subscription.
+ * clients that have an active subscription.
  */
 public class SubscriptionManager extends AbstractVerticle {
 
diff --git a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionService.java b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionService.java
index 64382f243e..c90ac19504 100644
--- a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionService.java
+++ b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionService.java
@@ -12,12 +12,12 @@
  */
 package tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.syncing;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.results.SyncingResult;
 import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.Subscription;
 import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.SubscriptionManager;
 import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.request.SubscriptionType;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 
 public class SyncingSubscriptionService {
 
diff --git a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheckTest.java b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheckTest.java
index b5856c4263..ca8e6472b1 100644
--- a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheckTest.java
+++ b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/health/ReadinessCheckTest.java
@@ -16,10 +16,10 @@
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.jsonrpc.health.HealthService.ParamSource;
 import tech.pegasys.pantheon.ethereum.p2p.network.P2PNetwork;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -141,6 +141,7 @@ public void shouldNotBeReadyWhenCustomMaxBlocksBehindIsInvalid() {
   }
 
   private Optional<SyncStatus> createSyncStatus(final int currentBlock, final int highestBlock) {
-    return Optional.of(new SyncStatus(0, currentBlock, highestBlock));
+    return Optional.of(
+        new tech.pegasys.pantheon.ethereum.core.SyncStatus(0, currentBlock, highestBlock));
   }
 }
diff --git a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/EthSyncingTest.java b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/EthSyncingTest.java
index 7425a64ccb..5f41b4f158 100644
--- a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/EthSyncingTest.java
+++ b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/EthSyncingTest.java
@@ -17,12 +17,12 @@
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.when;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.JsonRpcRequest;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.response.JsonRpcResponse;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.response.JsonRpcSuccessResponse;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.results.SyncingResult;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 
 import java.util.Optional;
 
@@ -66,7 +66,8 @@ public void shouldReturnFalseWhenSyncStatusIsEmpty() {
   @Test
   public void shouldReturnExpectedValueWhenSyncStatusIsNotEmpty() {
     final JsonRpcRequest request = requestWithParams();
-    final SyncStatus expectedSyncStatus = new SyncStatus(0, 1, 2);
+    final SyncStatus expectedSyncStatus =
+        new tech.pegasys.pantheon.ethereum.core.SyncStatus(0, 1, 2);
     final JsonRpcResponse expectedResponse =
         new JsonRpcSuccessResponse(request.getId(), new SyncingResult(expectedSyncStatus));
     final Optional<SyncStatus> optionalSyncStatus = Optional.of(expectedSyncStatus);
diff --git a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionServiceTest.java b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionServiceTest.java
index 830ec0d2ca..2ed3b407ff 100644
--- a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionServiceTest.java
+++ b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/websocket/subscription/syncing/SyncingSubscriptionServiceTest.java
@@ -20,10 +20,10 @@
 
 import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
-import tech.pegasys.pantheon.ethereum.core.Synchronizer.SyncStatusListener;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.results.SyncingResult;
 import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.SubscriptionManager;
 import tech.pegasys.pantheon.ethereum.jsonrpc.websocket.subscription.request.SubscriptionType;
+import tech.pegasys.pantheon.plugin.services.PantheonEvents.SyncStatusListener;
 
 import java.util.Collections;
 import java.util.List;
@@ -69,7 +69,7 @@ public void shouldSendSyncStatusWhenReceiveSyncStatus() {
         .when(subscriptionManager)
         .notifySubscribersOnWorkerThread(any(), any(), any());
 
-    syncStatusListener.onSyncStatus(syncStatus);
+    syncStatusListener.onSyncStatusChanged(syncStatus);
 
     verify(subscriptionManager)
         .sendMessage(eq(subscription.getSubscriptionId()), eq(expectedSyncingResult));
@@ -91,7 +91,7 @@ public void shouldSendNotSyncingStatusWhenReceiveSyncStatusAtHead() {
         .when(subscriptionManager)
         .notifySubscribersOnWorkerThread(any(), any(), any());
 
-    syncStatusListener.onSyncStatus(syncStatus);
+    syncStatusListener.onSyncStatusChanged(syncStatus);
 
     verify(subscriptionManager)
         .sendMessage(eq(subscription.getSubscriptionId()), any(NotSynchronisingResult.class));
diff --git a/ethereum/permissioning/src/main/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProvider.java b/ethereum/permissioning/src/main/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProvider.java
index 9493c132fb..e531d0bfc0 100644
--- a/ethereum/permissioning/src/main/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProvider.java
+++ b/ethereum/permissioning/src/main/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProvider.java
@@ -14,11 +14,11 @@
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
-import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.p2p.peers.EnodeURL;
 import tech.pegasys.pantheon.ethereum.permissioning.node.NodePermissioningProvider;
 import tech.pegasys.pantheon.metrics.PantheonMetricCategory;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 import tech.pegasys.pantheon.plugin.services.MetricsSystem;
 import tech.pegasys.pantheon.plugin.services.metrics.Counter;
 
diff --git a/ethereum/permissioning/src/test/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProviderTest.java b/ethereum/permissioning/src/test/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProviderTest.java
index c62fc53159..3fdbaa69da 100644
--- a/ethereum/permissioning/src/test/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProviderTest.java
+++ b/ethereum/permissioning/src/test/java/tech/pegasys/pantheon/ethereum/permissioning/node/provider/SyncStatusNodePermissioningProviderTest.java
@@ -21,10 +21,10 @@
 
 import tech.pegasys.pantheon.ethereum.core.SyncStatus;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
-import tech.pegasys.pantheon.ethereum.core.Synchronizer.SyncStatusListener;
 import tech.pegasys.pantheon.ethereum.p2p.peers.EnodeURL;
 import tech.pegasys.pantheon.metrics.PantheonMetricCategory;
 import tech.pegasys.pantheon.plugin.services.MetricsSystem;
+import tech.pegasys.pantheon.plugin.services.PantheonEvents.SyncStatusListener;
 import tech.pegasys.pantheon.plugin.services.metrics.Counter;
 
 import java.util.ArrayList;
@@ -104,7 +104,7 @@ public void before() {
 
   @Test
   public void whenIsNotInSyncHasReachedSyncShouldReturnFalse() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 2));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 2));
 
     assertThat(provider.hasReachedSync()).isFalse();
     assertThat(syncGauge.getAsInt()).isEqualTo(0);
@@ -112,7 +112,7 @@ public void whenIsNotInSyncHasReachedSyncShouldReturnFalse() {
 
   @Test
   public void whenInSyncHasReachedSyncShouldReturnTrue() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 1));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 1));
 
     assertThat(provider.hasReachedSync()).isTrue();
     assertThat(syncGauge.getAsInt()).isEqualTo(1);
@@ -120,22 +120,22 @@ public void whenInSyncHasReachedSyncShouldReturnTrue() {
 
   @Test
   public void whenInSyncChangesFromTrueToFalseHasReachedSyncShouldReturnTrue() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 2));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 2));
     assertThat(provider.hasReachedSync()).isFalse();
     assertThat(syncGauge.getAsInt()).isEqualTo(0);
 
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 2, 1));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 2, 1));
     assertThat(provider.hasReachedSync()).isTrue();
     assertThat(syncGauge.getAsInt()).isEqualTo(1);
 
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 2, 3));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 2, 3));
     assertThat(provider.hasReachedSync()).isTrue();
     assertThat(syncGauge.getAsInt()).isEqualTo(1);
   }
 
   @Test
   public void whenHasNotSyncedNonBootnodeShouldNotBePermitted() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 2));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 2));
     assertThat(provider.hasReachedSync()).isFalse();
     assertThat(syncGauge.getAsInt()).isEqualTo(0);
 
@@ -149,7 +149,7 @@ public void whenHasNotSyncedNonBootnodeShouldNotBePermitted() {
 
   @Test
   public void whenHasNotSyncedBootnodeIncomingConnectionShouldNotBePermitted() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 2));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 2));
     assertThat(provider.hasReachedSync()).isFalse();
     assertThat(syncGauge.getAsInt()).isEqualTo(0);
 
@@ -163,7 +163,7 @@ public void whenHasNotSyncedBootnodeIncomingConnectionShouldNotBePermitted() {
 
   @Test
   public void whenHasNotSyncedBootnodeOutgoingConnectionShouldBePermitted() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 2));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 2));
     assertThat(provider.hasReachedSync()).isFalse();
     assertThat(syncGauge.getAsInt()).isEqualTo(0);
 
@@ -177,7 +177,7 @@ public void whenHasNotSyncedBootnodeOutgoingConnectionShouldBePermitted() {
 
   @Test
   public void whenHasSyncedIsPermittedShouldReturnTrue() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 1));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 1));
     assertThat(provider.hasReachedSync()).isTrue();
     assertThat(syncGauge.getAsInt()).isEqualTo(1);
 
@@ -191,7 +191,7 @@ public void whenHasSyncedIsPermittedShouldReturnTrue() {
 
   @Test
   public void syncStatusPermissioningCheckShouldIgnoreEnodeURLDiscoveryPort() {
-    syncStatusListener.onSyncStatus(new SyncStatus(0, 1, 2));
+    syncStatusListener.onSyncStatusChanged(new SyncStatus(0, 1, 2));
     assertThat(provider.hasReachedSync()).isFalse();
 
     final EnodeURL bootnode =
diff --git a/pantheon/src/main/java/tech/pegasys/pantheon/cli/PantheonCommand.java b/pantheon/src/main/java/tech/pegasys/pantheon/cli/PantheonCommand.java
index 7071a8f127..a678c57b0d 100644
--- a/pantheon/src/main/java/tech/pegasys/pantheon/cli/PantheonCommand.java
+++ b/pantheon/src/main/java/tech/pegasys/pantheon/cli/PantheonCommand.java
@@ -822,8 +822,9 @@ private PantheonCommand startPlugins() {
     pantheonPluginContext.addService(
         PantheonEvents.class,
         new PantheonEventsImpl(
-            (pantheonController.getProtocolManager().getBlockBroadcaster()),
-            pantheonController.getTransactionPool()));
+            pantheonController.getProtocolManager().getBlockBroadcaster(),
+            pantheonController.getTransactionPool(),
+            pantheonController.getSyncState()));
     pantheonPluginContext.startPlugins();
     return this;
   }
diff --git a/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonController.java b/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonController.java
index 0b75529f32..84cacc53a7 100644
--- a/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonController.java
+++ b/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonController.java
@@ -21,6 +21,7 @@
 import tech.pegasys.pantheon.ethereum.core.PrivacyParameters;
 import tech.pegasys.pantheon.ethereum.core.Synchronizer;
 import tech.pegasys.pantheon.ethereum.eth.manager.EthProtocolManager;
+import tech.pegasys.pantheon.ethereum.eth.sync.state.SyncState;
 import tech.pegasys.pantheon.ethereum.eth.transactions.TransactionPool;
 import tech.pegasys.pantheon.ethereum.jsonrpc.RpcApi;
 import tech.pegasys.pantheon.ethereum.jsonrpc.internal.methods.JsonRpcMethod;
@@ -48,6 +49,7 @@ public class PantheonController<C> implements java.io.Closeable {
   private final MiningCoordinator miningCoordinator;
   private final PrivacyParameters privacyParameters;
   private final Runnable close;
+  private final SyncState syncState;
 
   PantheonController(
       final ProtocolSchedule<C> protocolSchedule,
@@ -56,18 +58,20 @@ public class PantheonController<C> implements java.io.Closeable {
       final GenesisConfigOptions genesisConfigOptions,
       final SubProtocolConfiguration subProtocolConfiguration,
       final Synchronizer synchronizer,
-      final JsonRpcMethodFactory additionalJsonRpcMethodsFactory,
-      final KeyPair keyPair,
+      final SyncState syncState,
       final TransactionPool transactionPool,
       final MiningCoordinator miningCoordinator,
       final PrivacyParameters privacyParameters,
-      final Runnable close) {
+      final Runnable close,
+      final JsonRpcMethodFactory additionalJsonRpcMethodsFactory,
+      final KeyPair keyPair) {
     this.protocolSchedule = protocolSchedule;
     this.protocolContext = protocolContext;
     this.ethProtocolManager = ethProtocolManager;
     this.genesisConfigOptions = genesisConfigOptions;
     this.subProtocolConfiguration = subProtocolConfiguration;
     this.synchronizer = synchronizer;
+    this.syncState = syncState;
     this.additionalJsonRpcMethodsFactory = additionalJsonRpcMethodsFactory;
     this.keyPair = keyPair;
     this.transactionPool = transactionPool;
@@ -126,6 +130,10 @@ public Map<String, JsonRpcMethod> getAdditionalJsonRpcMethods(
     return additionalJsonRpcMethodsFactory.createJsonRpcMethods(enabledRpcApis);
   }
 
+  public SyncState getSyncState() {
+    return syncState;
+  }
+
   public static class Builder {
 
     public PantheonControllerBuilder<?> fromEthNetworkConfig(
diff --git a/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonControllerBuilder.java b/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonControllerBuilder.java
index c855fbd862..576d5b1895 100644
--- a/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonControllerBuilder.java
+++ b/pantheon/src/main/java/tech/pegasys/pantheon/controller/PantheonControllerBuilder.java
@@ -323,8 +323,7 @@ public PantheonController<C> build() throws IOException {
         genesisConfig.getConfigOptions(genesisConfigOverrides),
         subProtocolConfiguration,
         synchronizer,
-        additionalJsonRpcMethodFactory,
-        nodeKeys,
+        syncState,
         transactionPool,
         miningCoordinator,
         privacyParameters,
@@ -338,7 +337,9 @@ public PantheonController<C> build() throws IOException {
           } catch (final IOException e) {
             LOG.error("Failed to close storage provider", e);
           }
-        });
+        },
+        additionalJsonRpcMethodFactory,
+        nodeKeys);
   }
 
   protected void prepForBuild() {}
diff --git a/pantheon/src/main/java/tech/pegasys/pantheon/services/PantheonEventsImpl.java b/pantheon/src/main/java/tech/pegasys/pantheon/services/PantheonEventsImpl.java
index db2a27f079..da78154ba2 100644
--- a/pantheon/src/main/java/tech/pegasys/pantheon/services/PantheonEventsImpl.java
+++ b/pantheon/src/main/java/tech/pegasys/pantheon/services/PantheonEventsImpl.java
@@ -12,66 +12,65 @@
  */
 package tech.pegasys.pantheon.services;
 
-import tech.pegasys.pantheon.ethereum.core.Block;
-import tech.pegasys.pantheon.ethereum.core.Transaction;
 import tech.pegasys.pantheon.ethereum.eth.sync.BlockBroadcaster;
+import tech.pegasys.pantheon.ethereum.eth.sync.state.SyncState;
 import tech.pegasys.pantheon.ethereum.eth.transactions.TransactionPool;
 import tech.pegasys.pantheon.plugin.services.PantheonEvents;
 
 public class PantheonEventsImpl implements PantheonEvents {
   private final BlockBroadcaster blockBroadcaster;
   private final TransactionPool transactionPool;
+  private final SyncState syncState;
 
   public PantheonEventsImpl(
-      final BlockBroadcaster blockBroadcaster, final TransactionPool transactionPool) {
+      final BlockBroadcaster blockBroadcaster,
+      final TransactionPool transactionPool,
+      final SyncState syncState) {
     this.blockBroadcaster = blockBroadcaster;
     this.transactionPool = transactionPool;
+    this.syncState = syncState;
   }
 
   @Override
-  public Object addNewBlockPropagatedListener(final NewBlockPropagatedListener listener) {
+  public long addBlockPropagatedListener(final BlockPropagatedListener listener) {
     return blockBroadcaster.subscribePropagateNewBlocks(
-        block -> dispatchNewBlockPropagatedMessage(block, listener));
+        block -> listener.newBlockPropagated(block.getHeader()));
   }
 
   @Override
-  public void removeNewBlockPropagatedListener(final Object listenerIdentifier) {
-    if (listenerIdentifier instanceof Long) {
-      blockBroadcaster.unsubscribePropagateNewBlocks((Long) listenerIdentifier);
-    }
+  public void removeBlockPropagatedListener(final long listenerIdentifier) {
+    blockBroadcaster.unsubscribePropagateNewBlocks(listenerIdentifier);
   }
 
-  private void dispatchNewBlockPropagatedMessage(
-      final Block block, final NewBlockPropagatedListener listener) {
-    listener.newBlockPropagated(block.getHeader());
+  @Override
+  public long addTransactionAddedListener(final TransactionAddedListener listener) {
+    return transactionPool.subscribePendingTransactions(listener::onTransactionAdded);
   }
 
   @Override
-  public Object addNewTransactionAddedListener(final NewTransactionAddedListener listener) {
-    return transactionPool.subscribePendingTransactions(
-        transaction -> dispatchTransactionAddedMessage(transaction, listener));
+  public void removeTransactionAddedListener(final long listenerIdentifier) {
+    transactionPool.unsubscribePendingTransactions(listenerIdentifier);
   }
 
   @Override
-  public void removeNewTransactionAddedListener(final Object listenerIdentifier) {
-    if (listenerIdentifier instanceof Long) {
-      transactionPool.unsubscribePendingTransactions((Long) listenerIdentifier);
-    }
+  public long addTransactionDroppedListener(
+      final TransactionDroppedListener transactionDroppedListener) {
+    return transactionPool.subscribeDroppedTransactions(
+        transactionDroppedListener::onTransactionDropped);
   }
 
   @Override
-  public Object addNewTransactionDroppedListener(
-      final TransactionDroppedListener newTransactionDroppedListener) {
-    throw new UnsupportedOperationException();
+  public void removeTransactionDroppedListener(final long listenerIdentifier) {
+    transactionPool.unsubscribeDroppedTransactions(listenerIdentifier);
   }
 
   @Override
-  public void removeTransactionDroppedListener(final Object listenerIdentifier) {
-    throw new UnsupportedOperationException();
+  public long addSyncStatusListener(final SyncStatusListener syncStatusListener) {
+    return syncState.addSyncStatusListener(syncStatusListener);
   }
 
-  private void dispatchTransactionAddedMessage(
-      final Transaction transaction, final NewTransactionAddedListener listener) {
-    listener.newTransactionAdded(transaction);
+  @Override
+  public void removeSyncStatusListener(final long listenerIdentifier) {
+    syncState.removeSyncStatusListener(listenerIdentifier);
   }
 }
diff --git a/pantheon/src/test/java/tech/pegasys/pantheon/plugins/TestPantheonEventsPlugin.java b/pantheon/src/test/java/tech/pegasys/pantheon/plugins/TestPantheonEventsPlugin.java
index d2716fb456..9aee3803e2 100644
--- a/pantheon/src/test/java/tech/pegasys/pantheon/plugins/TestPantheonEventsPlugin.java
+++ b/pantheon/src/test/java/tech/pegasys/pantheon/plugins/TestPantheonEventsPlugin.java
@@ -34,7 +34,7 @@ public class TestPantheonEventsPlugin implements PantheonPlugin {
 
   private PantheonContext context;
 
-  private Optional<Object> subscriptionId;
+  private Optional<Long> subscriptionId;
   private final AtomicInteger blockCounter = new AtomicInteger();
   private File callbackDir;
 
@@ -50,7 +50,7 @@ public void start() {
     subscriptionId =
         context
             .getService(PantheonEvents.class)
-            .map(events -> events.addNewBlockPropagatedListener(this::onBlockAnnounce));
+            .map(events -> events.addBlockPropagatedListener(this::onBlockAnnounce));
     LOG.info("Listening with ID#" + subscriptionId);
   }
 
@@ -60,7 +60,7 @@ public void stop() {
         id ->
             context
                 .getService(PantheonEvents.class)
-                .ifPresent(pantheonEvents -> pantheonEvents.removeNewBlockPropagatedListener(id)));
+                .ifPresent(pantheonEvents -> pantheonEvents.removeBlockPropagatedListener(id)));
     LOG.info("No longer listening with ID#" + subscriptionId);
   }
 
diff --git a/pantheon/src/test/java/tech/pegasys/pantheon/services/PantheonEventsImplTest.java b/pantheon/src/test/java/tech/pegasys/pantheon/services/PantheonEventsImplTest.java
index 112eb1fe90..194984e79c 100644
--- a/pantheon/src/test/java/tech/pegasys/pantheon/services/PantheonEventsImplTest.java
+++ b/pantheon/src/test/java/tech/pegasys/pantheon/services/PantheonEventsImplTest.java
@@ -42,6 +42,7 @@
 import tech.pegasys.pantheon.ethereum.worldstate.WorldStateArchive;
 import tech.pegasys.pantheon.metrics.noop.NoOpMetricsSystem;
 import tech.pegasys.pantheon.plugin.data.BlockHeader;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 import tech.pegasys.pantheon.plugin.data.Transaction;
 import tech.pegasys.pantheon.testutil.TestClock;
 import tech.pegasys.pantheon.util.uint.UInt256;
@@ -66,7 +67,7 @@ public class PantheonEventsImplTest {
 
   @Mock private ProtocolSchedule<Void> mockProtocolSchedule;
   @Mock private ProtocolContext<Void> mockProtocolContext;
-  @Mock private SyncState mockSyncState;
+  private SyncState syncState;
   @Mock private EthPeers mockEthPeers;
   @Mock private EthContext mockEthContext;
   @Mock private EthMessages mockEthMessages;
@@ -109,17 +110,40 @@ public void setUp() {
             mockEthContext,
             TestClock.fixed(),
             new NoOpMetricsSystem(),
-            mockSyncState,
+            syncState,
             Wei.ZERO,
-            TransactionPoolConfiguration.builder().build());
+            TransactionPoolConfiguration.builder().txPoolMaxSize(1).build());
+    syncState = new SyncState(mockBlockchain, mockEthPeers);
 
-    serviceImpl = new PantheonEventsImpl(blockBroadcaster, transactionPool);
+    serviceImpl = new PantheonEventsImpl(blockBroadcaster, transactionPool, syncState);
+  }
+
+  @Test
+  public void syncStatusEventFiresAfterSubscribe() {
+    final AtomicReference<SyncStatus> result = new AtomicReference<>();
+    serviceImpl.addSyncStatusListener(result::set);
+
+    assertThat(result.get()).isNull();
+    syncState.publishSyncStatus();
+    assertThat(result.get()).isNotNull();
+  }
+
+  @Test
+  public void syncStatusEventDoesNotFireAfterUnsubscribe() {
+    final AtomicReference<SyncStatus> result = new AtomicReference<>();
+    final long id = serviceImpl.addSyncStatusListener(result::set);
+    syncState.publishSyncStatus();
+    assertThat(result.get()).isNotNull();
+    result.set(null);
+    serviceImpl.removeSyncStatusListener(id);
+    syncState.publishSyncStatus();
+    assertThat(result.get()).isNull();
   }
 
   @Test
   public void newBlockEventFiresAfterSubscribe() {
     final AtomicReference<BlockHeader> result = new AtomicReference<>();
-    serviceImpl.addNewBlockPropagatedListener(result::set);
+    serviceImpl.addBlockPropagatedListener(result::set);
 
     assertThat(result.get()).isNull();
     blockBroadcaster.propagate(generateBlock(), UInt256.of(1));
@@ -130,12 +154,13 @@ public void newBlockEventFiresAfterSubscribe() {
   @Test
   public void newBlockEventDoesNotFireAfterUnsubscribe() {
     final AtomicReference<BlockHeader> result = new AtomicReference<>();
-    final Object id = serviceImpl.addNewBlockPropagatedListener(result::set);
+    final long id = serviceImpl.addBlockPropagatedListener(result::set);
 
     assertThat(result.get()).isNull();
     blockBroadcaster.propagate(generateBlock(), UInt256.of(1));
 
-    serviceImpl.removeNewBlockPropagatedListener(id);
+    assertThat(result.get()).isNotNull();
+    serviceImpl.removeBlockPropagatedListener(id);
     result.set(null);
 
     blockBroadcaster.propagate(generateBlock(), UInt256.of(1));
@@ -149,15 +174,14 @@ public void propagationWithoutSubscriptionsCompletes() {
 
   @Test
   public void newBlockEventUselessUnsubscribesCompletes() {
-    serviceImpl.removeNewBlockPropagatedListener("doesNotExist");
-    serviceImpl.removeNewBlockPropagatedListener(5);
-    serviceImpl.removeNewBlockPropagatedListener(5L);
+    serviceImpl.removeBlockPropagatedListener(5);
+    serviceImpl.removeBlockPropagatedListener(5L);
   }
 
   @Test
-  public void newTransactionEventFiresAfterSubscribe() {
+  public void transactionAddedEventFiresAfterSubscribe() {
     final AtomicReference<Transaction> result = new AtomicReference<>();
-    serviceImpl.addNewTransactionAddedListener(result::set);
+    serviceImpl.addTransactionAddedListener(result::set);
 
     assertThat(result.get()).isNull();
     transactionPool.addLocalTransaction(TX1);
@@ -166,14 +190,15 @@ public void newTransactionEventFiresAfterSubscribe() {
   }
 
   @Test
-  public void newTransactionEventDoesNotFireAfterUnsubscribe() {
+  public void transactionAddedEventDoesNotFireAfterUnsubscribe() {
     final AtomicReference<Transaction> result = new AtomicReference<>();
-    final Object id = serviceImpl.addNewTransactionAddedListener(result::set);
+    final long id = serviceImpl.addTransactionAddedListener(result::set);
 
     assertThat(result.get()).isNull();
     transactionPool.addLocalTransaction(TX1);
+    assertThat(result.get()).isNotNull();
 
-    serviceImpl.removeNewTransactionAddedListener(id);
+    serviceImpl.removeTransactionAddedListener(id);
     result.set(null);
 
     transactionPool.addLocalTransaction(TX2);
@@ -181,10 +206,39 @@ public void newTransactionEventDoesNotFireAfterUnsubscribe() {
   }
 
   @Test
-  public void newTransactionEventUselessUnsubscribesCompletes() {
-    serviceImpl.removeNewTransactionAddedListener("doesNotExist");
-    serviceImpl.removeNewTransactionAddedListener(5);
-    serviceImpl.removeNewTransactionAddedListener(5L);
+  public void transactionAddedEventUselessUnsubscribesCompletes() {
+    serviceImpl.removeTransactionAddedListener(5);
+    serviceImpl.removeTransactionAddedListener(5L);
+  }
+
+  @Test
+  public void transactionDroppedEventFiresAfterSubscribe() {
+    final AtomicReference<Transaction> result = new AtomicReference<>();
+    serviceImpl.addTransactionDroppedListener(result::set);
+
+    assertThat(result.get()).isNull();
+    // The max pool size is configured to 1 so adding two transactions should trigger a drop
+    transactionPool.addLocalTransaction(TX1);
+    transactionPool.addLocalTransaction(TX2);
+
+    assertThat(result.get()).isNotNull();
+  }
+
+  @Test
+  public void transactionDroppedEventDoesNotFireAfterUnsubscribe() {
+    final AtomicReference<Transaction> result = new AtomicReference<>();
+    final long id = serviceImpl.addTransactionDroppedListener(result::set);
+
+    assertThat(result.get()).isNull();
+    transactionPool.addLocalTransaction(TX1);
+    transactionPool.addLocalTransaction(TX2);
+
+    assertThat(result.get()).isNotNull();
+    serviceImpl.removeTransactionAddedListener(id);
+    result.set(null);
+
+    transactionPool.addLocalTransaction(TX2);
+    assertThat(result.get()).isNull();
   }
 
   private Block generateBlock() {
diff --git a/plugin-api/build.gradle b/plugin-api/build.gradle
index 6c2bad3b13..898cd952bf 100644
--- a/plugin-api/build.gradle
+++ b/plugin-api/build.gradle
@@ -56,7 +56,7 @@ Calculated : ${currentHash}
 tasks.register('checkAPIChanges', FileStateChecker) {
   description = "Checks that the API for the Plugin-API project does not change without deliberate thought"
   files = sourceSets.main.allJava.files
-  knownHash = 'PBo0D4R6/1EYXEn+k0nmWHW4TkklUWQbQGNqgWzslfw='
+  knownHash = 'j39vjVpNEK0kTpk/MLK8BHnqkFoRO9BWajrm9WoejWM='
 }
 check.dependsOn('checkAPIChanges')
 
diff --git a/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/data/SyncStatus.java b/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/data/SyncStatus.java
new file mode 100644
index 0000000000..753972b325
--- /dev/null
+++ b/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/data/SyncStatus.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2019 ConsenSys AG.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package tech.pegasys.pantheon.plugin.data;
+
+import tech.pegasys.pantheon.plugin.Unstable;
+
+@Unstable
+public interface SyncStatus {
+
+  /**
+   * Get the height of the block at which this synchronization attempt began.
+   *
+   * @return height of the block at which this synchronization attempt began.
+   */
+  long getStartingBlock();
+
+  /**
+   * Get the height of the last block the synchronizer received
+   *
+   * @return the height of the last block the synchronizer received
+   */
+  long getCurrentBlock();
+
+  /**
+   * Get the height of the highest known block.
+   *
+   * @return the height of the highest known block.
+   */
+  long getHighestBlock();
+
+  /**
+   * Checks if the synchronizer is within a default sync tolerance of the highest known block
+   *
+   * @return true if it is within the tolerance, false otherwise
+   */
+  boolean inSync();
+}
diff --git a/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/services/PantheonEvents.java b/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/services/PantheonEvents.java
index 18a99fa343..344364917d 100644
--- a/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/services/PantheonEvents.java
+++ b/plugin-api/src/main/java/tech/pegasys/pantheon/plugin/services/PantheonEvents.java
@@ -14,6 +14,7 @@
 
 import tech.pegasys.pantheon.plugin.Unstable;
 import tech.pegasys.pantheon.plugin.data.BlockHeader;
+import tech.pegasys.pantheon.plugin.data.SyncStatus;
 import tech.pegasys.pantheon.plugin.data.Transaction;
 
 /**
@@ -22,10 +23,13 @@
  * <p>Currently supported events
  *
  * <ul>
- *   <li><b>newBlockPropagated</b> - Fired when a new block header has been received and validated
- *       and is about to be sent out to other peers, but before the body of the block has been
- *       evaluated and validated.
- *   <li><b>newTransactionAdded</b> - Fired when a new transaction has been added to the node.
+ *   <li><b>BlockPropagated</b> - Fired when a new block header has been received and validated and
+ *       is about to be sent out to other peers, but before the body of the block has been evaluated
+ *       and validated.
+ *   <li><b>TransactionAdded</b> - Fired when a new transaction has been added to the node.
+ *   <li><b>TransactionDropped</b> - Fired when a new transaction has been dropped from the node.
+ *   <li><b>Logs</b> - Fired when a new block containing logs is received.
+ *   <li><b>SynchronizerStatus </b> - Fired when the status of the synchronizer changes.
  * </ul>
  */
 @Unstable
@@ -34,52 +38,67 @@ public interface PantheonEvents {
   /**
    * Add a listener watching new blocks propagated.
    *
-   * @param newBlockPropagatedListener The listener that will accept a BlockHeader as the event.
+   * @param blockPropagatedListener The listener that will accept a BlockHeader as the event.
    * @return an object to be used as an identifier when de-registering the event.
    */
-  Object addNewBlockPropagatedListener(NewBlockPropagatedListener newBlockPropagatedListener);
+  long addBlockPropagatedListener(BlockPropagatedListener blockPropagatedListener);
 
   /**
    * Remove the blockAdded listener from pantheon notifications.
    *
    * @param listenerIdentifier The instance that was returned from addBlockAddedListener;
    */
-  void removeNewBlockPropagatedListener(Object listenerIdentifier);
+  void removeBlockPropagatedListener(long listenerIdentifier);
 
   /**
    * Add a listener watching new transactions added to the node.
    *
-   * @param newTransactionAddedListener The listener that will accept the Transaction object as the
+   * @param transactionAddedListener The listener that will accept the Transaction object as the
    *     event.
    * @return an object to be used as an identifier when de-registering the event.
    */
-  Object addNewTransactionAddedListener(NewTransactionAddedListener newTransactionAddedListener);
+  long addTransactionAddedListener(TransactionAddedListener transactionAddedListener);
 
   /**
    * Remove the blockAdded listener from pantheon notifications.
    *
-   * @param listenerIdentifier The instance that was returned from addNewTransactionAddedListener;
+   * @param listenerIdentifier The instance that was returned from addTransactionAddedListener;
    */
-  void removeNewTransactionAddedListener(Object listenerIdentifier);
+  void removeTransactionAddedListener(long listenerIdentifier);
 
   /**
    * Add a listener watching dropped transactions.
    *
-   * @param newTransactionDroppedListener The listener that will accept the Transaction object as
-   *     the event.
+   * @param transactionDroppedListener The listener that will accept the Transaction object as the
+   *     event.
    * @return an object to be used as an identifier when de-registering the event.
    */
-  Object addNewTransactionDroppedListener(TransactionDroppedListener newTransactionDroppedListener);
+  long addTransactionDroppedListener(TransactionDroppedListener transactionDroppedListener);
 
   /**
    * Remove the transactionDropped listener from pantheon notifications.
    *
    * @param listenerIdentifier The instance that was returned from addTransactionDroppedListener;
    */
-  void removeTransactionDroppedListener(Object listenerIdentifier);
+  void removeTransactionDroppedListener(long listenerIdentifier);
+
+  /**
+   * Add a listener watching the synchronizer status.
+   *
+   * @param syncStatusListener The listener that will accept the SyncStatus object as the event.
+   * @return an object to be used as an identifier when de-registering the event.
+   */
+  long addSyncStatusListener(SyncStatusListener syncStatusListener);
+
+  /**
+   * Remove the logs listener from pantheon notifications.
+   *
+   * @param listenerIdentifier The instance that was returned from addTransactionDroppedListener;
+   */
+  void removeSyncStatusListener(long listenerIdentifier);
 
   /** The listener interface for receiving new block propagated events. */
-  interface NewBlockPropagatedListener {
+  interface BlockPropagatedListener {
 
     /**
      * Invoked when a new block header has been received and validated and is about to be sent out
@@ -88,20 +107,20 @@ interface NewBlockPropagatedListener {
      * <p>The block may not have been imported to the local chain yet and may fail later
      * validations.
      *
-     * @param newBlockHeader the new block header.
+     * @param blockHeader the new block header.
      */
-    void newBlockPropagated(BlockHeader newBlockHeader);
+    void newBlockPropagated(BlockHeader blockHeader);
   }
 
   /** The listener interface for receiving new transaction added events. */
-  interface NewTransactionAddedListener {
+  interface TransactionAddedListener {
 
     /**
      * Invoked when a new transaction has been added to the node.
      *
      * @param transaction the new transaction.
      */
-    void newTransactionAdded(Transaction transaction);
+    void onTransactionAdded(Transaction transaction);
   }
 
   /** The listener interface for receiving transaction dropped events. */
@@ -112,6 +131,17 @@ interface TransactionDroppedListener {
      *
      * @param transaction the dropped transaction.
      */
-    void newTransactionDropped(Transaction transaction);
+    void onTransactionDropped(Transaction transaction);
+  }
+
+  /** The listener interface for receiving sync status events. */
+  interface SyncStatusListener {
+
+    /**
+     * Invoked when the synchronizer status changes
+     *
+     * @param syncStatus the sync status
+     */
+    void onSyncStatusChanged(SyncStatus syncStatus);
   }
 }