The Empeg uses a StrongARM.
The software cannot run on the Psion. If notting else, then because of the difference in display and sound hardware.
Writing a controller for the psion should be relatively easy. You could use OPL and look at the example in the doccumentation for serial communication, and control the player via a serial cable.
There may also be possible to use IR to controll the player. I do not remember the state of IrDA-compliance in the Psion's OS.
(Let me know if you come up with something cool!)
Marius (Escort Cab + Mark II)