These are unspeakably kewl. The kit attaches to a bike hub and charges the ReeCharger while the bike is in motion: the turning motion of the dynamo in the bike hub generates power and generates electricity, much like a spinning wind turbine that generates power which is in turn collected by a generator.
You can either charge your devices directly as you ride, or charge a portable bike-mounted battery pack. The charging cable or battery pack can be used in real time while riding, for example to power a phone for use as a GPS. (The company also sells all sorts of bike mounts for phones and tablets, along with silicone sleeves to protect them from the elements.) Or you can charge the battery pack alone as you ride and then pop it into your bag when you get to your destination to serve as a portable power source.
Genius. Now since I don't bike to work, I need to figure out how to hook this up to my shoes for running power when I'm training for races... Wonder if I get enough mileage in to charge a phone?
Check out the Dynamo charge kit in action:
And here's a look at the Power pack:
(Source: Coolest Gadgets)