Meet the Chargeboard: an innovative skateboard that produces energy when you are skating and store it in a battery that you can use to charge your phone or do other cool things. It has two dynamos in the rear axles to generate 6V (each), which is then converted back to a 5V current. The energy is stored in a powerbox. Once you are done, you can plug your iPhone into the dock to charge it.
You get a external USB port to charge other mobile devices too. You can also connect your music player using the 3.5 mm audio jack to start playing audio through the speakers. 1 hour of cruising gives you enough power to charge your phone. There is a lot to like here. You can get yours on Kickstarter.