Continuance Rechargeable Battery with USB Interface for your Gadgets
AA batteries aren’t going away anytime soon. You can thank digital cameras, a variety of toys, and Xbox 360 controllers for that. However, there are probably now more USB powered gadgets than their are standard battery powered toys on the market today. Check this Continuance battery concept which allows you to power your compatible gadgets. On the side, though, is a USB port, which presumably allows you to rejuice them and power up gadgets that only take a USB plug, such as the iPhone or any other smartphone on the market.
I know there is a lot of thinking like “is the extra circuitry & connector in the battery will cause less capacity?” or “The efficiency lost when convert 1,2 V to 5V which is needed for most USB gadgets.” Not sure how the technology goes but it is a great concept just not that practical right now. [source]