The RemoteController class was introduced in the last version of Android, 4.4 KitKat. According to Google documentation, this class is used to control media playback, display and update media metadata and playback status, and is published by applications using the RemoteControlClient class. In plain English, this means that this class handles the behavior of media players.
It’s a new class used by Google, so it might be a bit problematic to understand how to use it. Luckily XDA Senior Member Dr.Alexander_Breen wrote a comprehensive guide, where he explains what should be done to successfully add this new function to your app. The guide is divided into five points to better understand the use of the new class. The final effect can be seen in a repository on Github, where Dr.Alexander_Breen pushed a sample of his code using this API.
You can find an answer to practically any question you may have in the original thread. This thread is oriented to experienced Android users / developers, so asking about adding this to PowerAmp is a bit pointless. Please keep that in mind, while you learn about the new RemoteController class. We wish you good luck in implementation this class into your personal projects._________