I have the J&M intercom system mounted up on my bike. I put in on before my florida trip this past spring so that my girl friend and I could communicate and since it is also a CD radio, Jordan and I could talk to my parents on their bike. (They have the same system)
It as an auxilary hookup that uses a mini-jack, so I plug in my ipod to it and turn the volume all the way up and then control the volume to the headsets with the dial on the unit.
I was very impressed with J&M's customer support when I called them to ask them about how I should pull my parents unit apart in order to try to clean off some sort of stain that wouldnt come off the case. He told me just to send it in and they would take care of it. The replaced the case, change the mother board out to a updated one and changed all the bottons as well, free of charge! He basicly got a brand new radio for free! They really stand behind their stuff.
I have lots of pictures of my install and would be glad to help you with anything if you decide to go with it.
-bryan