hi there,

I did some dbus-monitoring on the N900 and found that the following command pauses the media player:
dbus-send --dest=com.nokia.mafw.renderer.Mafw-Gst-Renderer-Plugin.gstrenderer /com/nokia/mafw/renderer/gstrenderer com.nokia.mafw.renderer.pause

I made (a quick) change in headphoned and it works.

I also tried with libplayback, but didn't succeed. I think that library should be used when you are creating your own player and is not really for controlling other players. Anyway, that is just my guess, because I can't get much from the documentation...