Here is test version handling PLAY like PLAY_PAUSE event.
But I am not sure this will work because no event looks like coming in response to your 2nd play/pause button press.
Also, I managed to implement it in my test app and it works perfectly _unless_ I interact with the user interface (MediaController class). Everything works as long as my app is in the background and I don't touch onscreen controls. Else they seem to "grab" focus from the BT listener.
edit: more specifically, calling the MediaController.show() is what seems to steal focus for my test app. It's as if the focus moves away from the UI to the media controller. If I leave it on screen, and click on a "settings" menu, returning focus to my activity, the key start working.
edit2: MX player shows the same behavior. I attached a new log, now you should see PLAY events after i've sent mx player to background with background play enabled