An undercover would love the following idea. An AA battery USB flash drive is a concept design by Wonchul Hwang. You will be able to use it to store your important data as well as using it as an AA battery whenever your gadget running out of battery power.
No info if the AA battery is the rechargeable type? Call it AA USB, would it be useful for nowadays mobile communication gadgets that mostly use the flat shape lithium ion rechargeable battery with power pack?
[ Source: Yanko Design ]