If you haven't experienced the joy of going 48 hours without charging your iPhone 4, you just might need to invest in a Mophie Juice Pack Air, a case that's built around a rechargeable battery that gives your iPhone a lot of extra time to party away from the outlet.
I have to admit that I was skeptical at first. The Juice Pack Air looks like it might bulk up the iPhone 4's slim design a bit. It also covers Apple's sacred proprietary port, which is a pet peeve of mine when it comes to accessorizing my phone. When that port is covered, I can guarantee you that I'm going to run into a situation where I'll need it (e.g. plugging into my FM transmitter in the car), and tearing a case off and on is always a pain in the butt.
I was pleasantly surprised with what I can only describe as a luxurious amount of extra battery time allowed by Mophie's Juice Pack. The case itself is well designed, lightweight, and doesn't stray too far from the iPhone 4's original lines. As for protection, the Juice Pack is relatively robust, provided you drop your phone on its back. If you happen to drop it face down, you're probably going to have problems. There's not much protection up front.
As for that proprietary port, the case has a mini USB port so you can sync and charge your phone at the same time. It's not going to work with my FM transmitter, but at least I don't have to take the case off every time I want to plug my phone into the computer.
The amount of extra life you're going to get out of the Juice Pack depends on how heavily you use your phone. Travelers and business users at conferences (hello, CTIA!), are probably the target audience for a device like this. Still, for those slackers out there who forget to charge their device overnight, the Juice Pack is a nice luxury for the (lazy or forgetful) daily user.
Mophie advertises that the Juice Pack can "virtually double" your iPhone 4's battery time. I found that to be pretty accurate. I was able to go more than two days without connecting my device to a computer or wall outlet. When my iPhone did run down, I flipped the toggle switch on the case that dumps the Juice Pack's juice into the main iPhone battery and it took about 45 minutes for my phone to return to a full charge.
Another nice feature is the four LED lights at the bottom of the case. Press a button and they display how much life you've got left in your Juice Pack, with one light being a quarter charge to four being a complete charge
The battery problem isn't going anywhere. While battery life has improved quite a bit in just a few short years, available real estate inside the smartphone itself is at a premium. While Apple was able to increase the size of the iPhone 4's battery, it was able to do so by moving the antenna to the outside of the device (and we all know how well that worked). It's worth noting that Apple is particularly dependent on external accessories like the Juice Pack because it's one of the few OEMs that doesn't offer a way for users to swap out batteries.
For at least the time being, external battery sources like Mophie's Juice Pack may be where it's at for those iPhone users who need to squeeze a few extra hours out of their phones before they have to plug in. What I'd really like to see is a best-of-both-worlds scenario, where a high-end case maker like Otterbox partners with a company like Mophie to create a case that not only gives you some extra battery time but also offers great protection.
In my opinion, the Mophie Juice Pack Air justifies its $80 price tag. The company boasts a variety of different solutions for Apple's iOS line of products, from battery cases to those like the Mophie Marketplace, which turns the iPhone into a credit card terminal.