Since the iPhone 4 has a completely different shape than the iPhone 3G/3GS, all those older cases don’t fit the new device. Unfortunately, this also includes external battery cases like the Mophie Juice Pack. We’ve been waiting for an announcement from Mophie since Apple made the iPhont 4 public, but there really hasn’t been any noise from them as to when we can expect an updated battery for the iPhone 4. That’s where the Mili PowerSpring 4 comes in. It shouses a 1600 mAh battery which basically doubles the battery life of your iPhone 4. It’s available now for £54.99 (or $85 on Amazon.)