Finally a battery case for the iPhone that does more than just add power to your phone. The Kensington BungeeAir Security Case sports a 1500mAh lithium polymer battery that should add about 4 extra hours of talk time to your iPhone 4. In addition to the battery you get a keyfob that will alert you via beeping/vibrating when you get out of range and will lock your phone. You also get a two position kickstand built-in to the case. Lastly, since the BungeeAir uses two-way communication you can use the phone to locate the keyfob which is hopefully attached to your keys.
Way to add some real features to an iPhone case Kensington. Video of the BungeeAir after the break.