Here is a pedal powered charger that lets you convert leg power into electric power to charge your smartphone or GoPro cameras on the go. The Ride-a-long charger is easy to install and capable of charging any USB powered device. As you ride, your rear wheel engages a generator that chargers a 1650 mAh battery. The battery is detachable.
Ride-a-long is fairly compact and does not get in your way as you ride your bike. It can charge iPhone, iPad, and Android devices as well as GoPro cameras. Sets you back $129.