Since the iPhone 4 form factor was such a radical redesign from the iPhone 3GS, one annoyance was that cases fitted for the previous device simply don’t fit the new one. Makes sense, but for us that meant parting with our Mophie Juice Pack, which we’ve been rocking for a couple of years. The great thing about it is that it’s basically a case that doubles the power of your iPhone, and it’s indispensable when you are out on the road or traveling. Mophie’s been saying that an iPhone 4 case is coming soon, but they’ve been scant on details, and it looks like a company called EXOGEAR has beat them to the punch with the Exolife iPhone 4 Rechargeable Battery Case. We’ve been using it for a while, and have our thoughts for you after the jump.