Hi Kevin, I would like to further follow up on this since I am exactly one of the developers who use PlayAndRecord + NowPlaying hacks, and now trying to migrate to use Push to Talk framework with its declared support of setAccessoryButtonEventsEnabled. In short, I tried the Bluetooth headset (Powerbeats Pro) and pressing the button on the device cannot trigger didBeginTransmittingFromSource in a straightforward sample project which use PushToTalk framework and channel joined. Pressing the talk button on system UI also worked. You did mention "wired headphones" in your comment but I did not have wired headphones with me so cannot verify. However, since both wired and bluetooth headsets are sending media events when pressing the button, I would expect it should also work for Bluetooth headset? My hacks of using NowPlaying center did work with Bluetooth headset when I press the button on it.