Anytime you step on the brakes, the generator collects power that it stores in an on-board battery. A sensor in the wheel’s hub can tell when your ride becomes strenuous, like when you’re heading uphill. The sensor then triggers an electric motor that boosts your forward pedaling power. The next time you hit the brakes the cycle starts all over.
The app then lets you share your data with friends through social networks, helping you keep track of your friends throughout the city. It also allows riders to anonymously share urban and environmental data collected by sensors in the wheel with other riders around the city, creating a centralized information hub that's constantly fed real time info by bikers spread across the landscape. It even lets you rack up “green miles” as you travel about, a system not unlike a frequent-flyer program that rewards you for logging time on your bike rather than a car, bus or train.
All of the sensors, instrumentation, batteries and motor are packed in the Copenhagen Wheel itself (which is actually just the hub), and a spoking method devised by the team allows the hub to mount on any bicycle rim, though there's no mention of how much weight it adds to your ride. The Copenhagen Wheel should hit the market within a year, retailing for between $500 and $1,000.
[CNET]