From Moixa energy UK comes the USBCell which are normal AA,batteries but with a difference. You dont have to charge them on a charger but on your USB port. Simply pop the lid to reveal a built in connector and charger and just plug it into any USB port to charge the battery. Which means you no longer have to carry packs of Alkaline batteries or a clunky charger. As you will never runs out of USB ports the USBCell will prove to be cost-effective and convenient for all battery-powered devices. Though currently available only in AA format, the company will soon launch a full range of standard formats, phone and camera batteries.

Moixa USBCELL brings truly portable power for devices. The USBCELL can be bought online (UK only) for £12.99 ($ 24.50) for two AA batteries.
Via - Fareastgizmos

Soon to be released phone battery.