[ame=http://www.youtube.com/watch?v=R1AzailvJB0]YouTube - iPhone ARider ver 0.3 by UEI / ZeptoTools[/ame]
video via Zeptotools
A Japanese firm has developed a prototype navigation system for cyclists using an iPhone 3GS and a helmet-mounted display. MAKE Online links to a video of the project by Ubiquitous Entertainment where the rider is shown with the iPhone in what looks like a pretty precarious mount on top of the helmet (which one colleague noted looked like a samurai's [ame="http://en.wikipedia.org/wiki/Chonmage"]chonmage[/ame] haircut).
Due to safety concerns, the developers suggested that the Scalar Corporation T3-A HMD should be retracted while riding. So it's definitely not ready for prime time, with the iPhone exposed to the elements on top of your helmet, and having to stop for directions. Still, it's an innovative use of the core functionality of the iPhone plus add-ons like the head-mounted display and an ADSP Bluetooth headset for voice control and for your cycling soundtrack.
Now all they need is a proximity sensor for warning you about drivers opening their doors in your path...