In case anyone's looking for them, here are the keycodes I recorded for the CE-RH2:
Volume up: 118
Volume Down: 119
Mute: 120
Play/Pause: 64
Stop: 68
Previous: 116
Next: 108
I'm trying to get it to work in Opie now; a less-than-ideal workaround for the moment is to map play to "space", previous to "Left", next to "Right", and stop to "escape"; this will at least work if mediaplayer is already open and has the focus (I think a better solution would be to capture these outside the player and send the appropriate signals; that way volume could be controlled outside the player, and hitting "play" could launch the player if necessary.. if anyone else has any clues on how to do this, let me know )