I did some checking on the Pioneer CD-CM1, and this is exactly what I've been looking for. All I need is something that triggers the cell mute line automatically when I get a call. After that, I can just use the Hijack extmute commands to switch to the AUX input.

Unfortunately, every picture of this thing neglects to show the actual plug at the end of the cable. The descriptions list the Pioneer models which work with the CD-CM1, but I want to know if I can adapt it to work with the Empeg's cell mute line. Do you know if this is possible, or do you know where I can get specific information on what signal the CD-CM1 puts out?