Cannondale bikes hired a design firm to render up some possible future features on their rides, one of which is a very interesting one called MetroPolite that has an iPod connector. An iPod seems like the last thing you want to be shoving into your ears when you're riding in a Metro area, seeing as bikes lose to cars when the latter accidentally hit the former, but the connector isn't just for that.
Based on the renderings, you can display a rear view camera on the screen (technically impossible) or use the iPod like a Nike+ device to track your bike workout (might also be impossible). Still, very cool if you're using this on rides that aren't through traffic. [Cannondale Community via Cannondale via Trend Hunter]