Credit: PowerGen

The RollerGen Power System attaches to bicycles (Either stationary or standard) and turns Pedal Power into Electric Power for Electronics Devices.  It powers cell phones, MP3 players, GPS units, anything powered by USB, the standard for modern electronic devices. Power is stored in a pocket sized miniature battery that has the dual USB output plugs.

It charges up 30 watts in a short 4-5 miles of riding. The unit fits bikes like a standard rear rack and has a spinning flywheel that contacts your tires. The only downside is that it costs $495.  Hit $99 and they will sell a ton of units.