Would you believe I joined this forum just for this thread?

I too have an e36 M3, although I don't have an empeg. I do however have a Zaurus SL-5500 which runs Linux, has a serial cable and has a headphone jack. I'm planning on turning it into an mp3 player since I no longer use it.

Shonky: I'm putting together the simple iBus interface tomorrow. Have you actually been able to read/write to the iBus thus far? What year is your M3 and what color is the iBus wire? I'm assuming you're using the CD Changer cable in the trunk? Best of luck on your project!