If all you want is bike 2 bike without intercom or complicated audio mixing (GPS, radar, etc.) then I suggest the Motocomm headset from
http://www.radiogadgets.com with a GMRS or FRS radio. GMRS on the bike is good for 1-3 miles range which is plenty. Motocomm also sells an optional audio patch that will allow you to plug in a Walkman or MP3 player. Add a Boosteroo to boost the music volume and you're all set for <$200 :-D
