I've got as couple of mates who swear by the Autocom units they have fitted ( R1150GS, FJR 1300 & R1200 land yacht ) both for rider / pillion as well as bike to bike, phone, MP3 & Sat nav inputs.
Must admit it's something I've been considering from the bike to bike angle when on long trips on the continent, but then again, who'd want to talk to me?
If you want some more input, try searching on one of the touring oriented forums like
ukgser forum [Edited on 7-11-2005 by Rushjob]