Found these on the NET.

Not a bad idea, but unsure if it will be a winner.

usbcell - revolutionary rechargeable usb battery that can charge from any USB port

cool, neat idea... the mAh rating is abit low.. but should suit less demanding stuff..

That looks like a lot of hastle to me. Most items of equipment use more than 1 battery and USB ports are generaly too close together to charge 2 of those batteries simultaneously. Waste of time me thinks.