i think lot of people (like me) don't use the default headphones that comes with the N900, so would be better to implement this functions on hardware keys. there is already an app to play/pause or skip track with the default headphones (which doesn't work with the handsfree that comes with my Nokia 5800) so better than bring remote control with default headphones (that already exists) or universal control with all headphones and handsfree (imposible), make your efforts on N900 hardware keys.

Other thing: what about switch volume keys functionality? (short press for volume and long for prev/next track) i think short press allows you to adjust the volume more precisely than long presses.
And camera button, long press for stop player? i think is innecesary if there's play/pause with short press, also the player has no touchscreen button for stop, so what about other use?