Want some extra talk/browsing time on your iPhone 4? All you'll have to sacrifice is your phone's sleek frame and rear. The Slim Exolife iPhone 4 case (via Giz) weighs 59 grams and includes a polycarbonate frame and a power meter. Exolife claims that this external battery will double your iPhone's battery life.
The ExoLife iPhone 4 case will set you back $90 and ships out on July 30. If you're interested, you can pre-order right here.