DavidB pointed out this interesting little gadget to me and I thought it was a really cool idea. I travel quite often and tend to run out of juice. I am not always conveniently around a wall charger so I have resorted to using a Case-Mate Fuel for my Bold. The PowerPak which comes out in November is essentially just a wall charger for any USB device with a built in battery so that it can store a charge.
That means you can always pump in that last bit of juice while on the go. I am not sure what the capacity will be but the idea of giving your wall charger a secondary purpose is appealing since you have to carry it around anyways. I always thought it would be really cool if laptops could perform the same function of charging a gadget while off. Some laptops do this when the power plug is in but I have yet to hear of one that does it without the power cable plugged into the wall.