I use this sony one:
http://www.sonystyle.ca/commerce/ser...=100057n100059
not specifically designed for helmets, but works great !! The mic / body of the system clips nicely to the chin cover of my helmet. Hooks up to my zumo 550 and motorola cell phone perfectly. No problem using the phone, and loud enough to hear the music at speed. Battery life is about 15 - 20 hours.
