And as MorphOS has a nice command for sending AREXX commands directly to programs.. this might look little cleaner:

RXCmd MPLAYER.1 "volume abs 50"

And as speaking of Mac mini as a media player... I've just configured my MorphOS on mini to be controlled with remote controller :) I don't need keyboard or mouse at all to be able watch DVDs or other videos, listening music or watch photos. Now it's easy to take mini with only remote control to other places etc.

I used MMKeyboard to map buttons as I want... DVD button starts DVD playing directly, music button opens AMPlifier with all my mp3s, photo button opens ShowGirls with my digital photo directory and video button opens Ambient drawer with my video files. I can browse and rotate pictures in SG.. and browse and start playing videos in Ambient etc.

Then I also have little arexx script to control all players with one script. Remote controller's play, pause, stop, prev, next and volume buttons work with all players (mplayer, amplifier, anr, songplayer, amigaamp).

BTW. I also tried another USB remote control device, but didn't get it work with Poseidon... it had option to control the mouse too, while this working device works as keyboard only. I'm guessing that keyboard+mouse combo devices don't work properly.. anyone knows anything about it?