Mophie Juice Pack
The Mophie Juice Pack is a battery pack that looks like a sleeve rather than a bulky battery pack. So you charge up the Juice Pack and your iPhone then the smart battery technology causes your phone to first draw from the Pack then once it is depleted it will draw from the iPhone's battery. The pack gives you up to 250 hours of standby time, 24 hours of music playback, 8 hours or talk time, 7 hours of video playback, and 6 hours of Internet use. This is a great way to extend the battery life of your iPhone without bulking it up.
Absolutely awesome. Ben outdid himself with this design.