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Headset control was written by the legendary qwerty12. He is gone now. He almost cracked complete control of the media player via the headset however he went bug house loco and burned out.

Your options are:

1. Stick to media players that use gstreamer as the backend as hset control is actually a gstreamer remote control.

2. Dig up Hset control version 0.2 (I think). Version 0.2 was actually a set of scripts and could be used to control mplayer and panucci(?). As it was just a set of scripts you could possibly bodge it to send the someplayer dbus play/pause instead of the gstreamer play/pause.