USB Rechargeable Battery

USBcell is a rechargeable battery that plugs in to any standard USB port.  With over 15 billion Alkaline batteries made and thrown away each year, USBCELL offers a eco-friendly alternative as can be re-used hundreds of times without the need for an additional charger or cable.

While a good idea in theory, there are still limitations, as can be gathered by the product's Amazon page:

1. Costs much more than a regular battery

2. Tendency to separate

3. Long charging time

4. Possibility of overcharging or burning out the computer's motherboard

but these seem to be problems that can be solved with product development.

Source: USBcell