I usually make android application using Xamarin (Yea! I feel much comfortable in c# ) so I picked Xamarin for android wear app. As making android app in Xamarin exactly same as compared to android development in official Android Studio or Eclipse. The plus point is that you can use many C# functions which is real beauty of Xamarin Studio. some high level advantages of Xamarin
- Xamarin technology allows you to keep Native UI across all three platforms.
- Xamarin is integrated with SDKs of all of the different operating systems
- Best Native experience app
- Single codebase share to all mobile platform
- You can use your c# powerful function like extension, delegate, lambda , Linq etc. in mobile development
At the moment using a 320x320 bitmap should cover all the bases for you.
Get more details on this in my article Article on Wearable device