I'm leaning towards trying out the Nady MRC-11X as a starter set. The intercom mode between the rider and passenger sound as though you could use it to allow both the rider and passenger to communicate as well as both to listen-in on any bike to bike communications.
It doesn't have Bluetooth, but I'm still not convinced I want to answer my cell phone while I'm cruising...
Anybody have any experience with this set?
http://www.amazon.com/Nady-MRC-11X-C.../dp/B0007D4TSE