GNOME Mplayer has a dbus interface

Signals it handles

Open			string:
OpenPlaylist	string:
OpenButton		string:		string:
Close
Play			
Pause
Stop
Prev
Next
FastForward
FastReverse
Quit
Terminate
Seek			double:
SetFullscreen	boolean:
SetInfo			string:
SetPercent		double:
SetProgressText	string:
SetShowControls	boolean:
Volume			double;
VolumeUp
VolumeDown
Ping


Path controls what items are controlled

Path			What is controlled
/				All gnome-mplayer windows, good for multihead
/pid/[pid]		Controls just the instance with pid=[pid]
/control/[cid]	Controls all instances with control id of [cid] set
/window/[wid]	Controls instance embedded in window id [wid]

Example dbus-send

Tell all windows to "Play"
dbus-send / com.gnome.mplayer.Play	

Tell window embedded in window 123 to Pause
dbus-send /window/123 com.gnome.mplayer.Pause	

Tell player with controlid of 456 to Open and Play /tmp/media.mov
dbus-send /control/456 com.gnome.mplayer.Open string:'/tmp/media.mov'

Seek to 400 seconds into the media file
dbus-send  --type=signal / com.gnome.mplayer.Seek double:400.0

Get the current position
dbus-send --print-reply --type=method_call --dest=com.gnome.mplayer / com.gnome.mplayer.GetTime

Get the currently playing URI
dbus-send --print-reply --type=method_call --dest=com.gnome.mplayer / com.gnome.mplayer.GetURI

Get the currently playing URI from a player with controlid of 456
dbus-send --print-reply --type=method_call --dest=com.gnome.mplayer.cid456 / com.gnome.mplayer.GetURI