The Mophie Juice Pack Air ($80) is the best iPhone battery extender to date, better then the original Mophie Juice Pack. It features a much more slim and sleek design and will add up to 270 hours of battery life. Even though it may add less battery time then the original Juice Pack, it is clearly more of a case than a battery extender like the early version. It comes in black, purple, and white and is available now for pre-order on their website. Expect it to ship out sometime in the coming months.