We all have USB keys and we all use AA batteries so designer Wonchul Hwang has married them into one concept. Unfortunatly this is still only a concept but I'm sure someone will borrow the idea and create a kickstarter for it...
You plug it into a PC and use it as portable storage which also charges it. If you're stuck and need a AA battery for a flashlight or radio, just pull it from the PC and drop it into the device.
Source: instash