When we first saw this charger, we thought it was a prototype from Make:, which actually has a kit available for $19.99.  It might have started out that way, but now is in fact a viable product that someone has constructed for you. It operates like any other charger with a USB port which is powered by 2 AA batteries (including rechargeable ones.) Use it on your iPod, MP3 player, cell phone, camera, etc. for a charge that they claim is 2x curiously stronger than that of a standard USB charge. The mini boost device is $37.99 at Esty with an optional low-battery indicator for $7.99.