Incipio has introduced their first ever battery pack case for the iPhone 4 called the offGRID today at gdgt's event in San Francisco. The offGRID battery pack slider case promises to double your iPhone 4's battery life using it's ultra slim 1450mAh battery. All of this power is packed into a slim case with a thickness of just 6mm with a weight of only two ounces, impressive to say the least.
You can charge and sync your iPhone 4 while it's inside the offGRID case using the supplied mini USB cable, the blue battery status indicator LED's at the front will tell you how much juice you have left. You can pick up the offGRID in early-to-mid December for $69.99.