Myself i have an autocom kit under the seat which has:
Phone link, MP3 Player link, Intercom radio for bike to bike.
x 2 Headset sockets with microphones.

Ideal for a ride out as mp3 player volume goes quiet when on phone or talking via bike to bike or rider to pillion.

Not that I've had to use bike to bike yet or rider to pillion. I just enjoy the music...