The BioLogic ReeCharge Power is a personal power system that can charge most any USB-chargeable device such as smartphones, GPS units or cameras. Perfect if you need to keep your gadgets charged, eg. during long bike tours. Inside is a lithium polymer battery that can be charged by wall outlet, through the included micro-USB cable from a computer and, most importantly, any bicycle with a hub dynamo.
Once you attach the BioLogic ReeCharge Power Pack to the bottom of the power regulator which is itself attached to the bicycle hub dynamo, the device captures and stores the green energy created by the generator in the hub. The cable from the top of the regulator has a connector at the end, which I believe will plug straight into an iphone so could be used to charge an iphone as you ride, without the Power Pack.