Wow, that looks like just the ticket. Connect that chip to an Arduino chip with an RS-232 output, and that might just work. Wow. All it would need is the software to send the serial commands to the empeg for next track (I think it's "n <cr>" for example), previous track, and play/pause (I forget which one is "p <cr>" and which one is something else).

You could either implement it internally to the empeg (soldering to the serial pins and to the aux output pins inside the player), or, if you could condense the whole thing to a single PCB that was small enough, make it a single flat module that plugs into the lower back portion of the player on the outside, connecting to the external serial port and aux plugs, tucking in just beneath the dock connector. If it were just the right size and shape, it could still fit even when docked. I think there's a pretty good amount of space in that area between the player and the dock.

Super interesting idea. This takes it from a realm of "this is out of my league" to "within my grasp if I only had the time". I've created Arduino interface circuits before, including all the PCB design and prototyping, and found the process fascinating and fun.
_________________________
Tony Fabris