Battery life is the iPhone's kryptonite. It sucks away all of Apple's supergadget powers so you're left with a pocket-sized brick after less than a day's use. The Dexim S7 is like a Kryptonite shield for your iPhone, adding a heap of battery life, while also doubling as your iPhone's very own ice palace (it has a kickstand so you can watch movies handsfree).
The S7's built-in 1500mAh Lithium Polymer battery will give you up to 4.5 hrs talk time, plus an extra nine hours video time or an extra 9 hours gaming time. It'll work with both the iPhone 3G and the 3GS, and charges via USB. It'll set you back $90.