+1 on the Sena SMH10. You can actually have up to 4 people talking, full duplex. I've used mine a fair bit as a 3-way intercom. Plus listening to music and talking on the phone. Works great.
'09 R12GS, '05 GSX-R1000
Iron Butt # 4999, WERA/CCS EX # 666 (currently, expired), AMA Life Member
Racer, Drummer, Bassist, Software Engineer