Android supports hardware play / pause buttons on headsets and attached devices. I am trying to find a way to test support for those devices on an emulator. The Android documentation talks about how to add support for hardware playback controls, but, unfortunately, I can't find documentation of how to emulate them. Thanks!
You can send keyevents using adb
adb shell input keyevent <keycode>
keycode for play - 126, pause - 85 (see KeyEvent)