http://www.reconinstruments.com/
Apparently this company is doing some beta testing of a clip (along the lines of Bluetooth comms sets) on HUD for motorcycle helmets. It sounds interesting, but I wonder even if the display is in your helmet, how distracting would it be, and how much better is it than a normal set of gauges plus a bolt on GPS?
Looking through their manual it looks like they have the bluetooth, gps nav, audio, android connect, and interface set up already. it shouldnt take much to adapt it to a helmet as a platform and make some software adjustments to adapt to the needs of the motorcycling community.