Really useful: a rechargeable battery - the USBcell - which can be used like a normal battery, and can be recharged simply by plugging it into a USB port.

Charging
Charge anywhere from any accessible powered USB.

Portability
No need for a separate charger or cables when travelling. Built in intelligent USB charger.

swap and Play
Easily charge cells in your game station and just swap over to continue play.

Top-Up
Charging for just a few minutes provides extra hours of instant use for most input devices.

Also can be charged in approved NiMH Chargers.

USBcell will be available in a AAA format with a mini-USB connector and also with a folding full-size USB, and with convertors. Check out this page for more information.