Heart Beats does not and never will collect any information, whether that be personal information, how you use the app, or otherwise. Playlists and album art are generated based on your device's local library, and nothing in the app ever leaves your device.
If you have opted into sharing crash reports/session data with Apple, then Apple may share some entirely anonymized information with the developer in accordance with their privacy policy. This data is only used to fix bugs and improve the app.
Heart Beats does not have a business model. This is a free app made for personal use, distributed on the App Store so that others might enjoy it too. No information associated with the app will ever be sold or transferred to another party.
The source code available here is identical to what is built and sent to the App Store. You are also welcome to build it yourself, but will need to check back here manually for updates.