For all the smartphone users in this world who argue that the iPhone 4's 1420mAh Li-Polymer battery simply isn't enough for day-to-day productivity tasks and traveling purposes, Mophie claims that its external rechargeable battery will double the battery life of the iPhone while offering the full protection of a hard-shell case. Cited as the thinnest rechargeable battery case on the market, the product's ultra-thin, light-weight, low-profile design features pass-through USB 2.0 charging and allows the smartphone to be synced with iTunes. Unfortunately, it does not allow the device to be docked in the official Apple iPhone 4 Dock accessory.
Like its predecessor for the iPhone 3G and iPhone 3GS, the Mophie Juice Pack Air for iPhone 4 features an integrated 4-LED charge indicator and a standby switch that turns off the external battery pack and allows the smartphone's internal battery to do all the work if preferred.
Engadget currently has a prototype device in hand, and judging by its looks, the product will add about a half-inch of length when connected to an iPhone 4, but it retains most of the device's ultra-thin form factor and shouldn't affect the ease of sliding the device in and out of pockets as many third-party rubber cases tend to behave.
The Mophie Juice Pack Air for iPhone 4 should be on sale as early as next week for $79.