Apple's switchover to the Lightning connector, and the subsequent tightening of its hold on the electronic accessory field, has resulted in a delay of battery cases for the iPhone 5. uNu has taken a unique approach to this issue with its Ecopak Detachable Snap-On Case + Extended Battery ($80). Rather than a case with a built-in battery and an electronic connection, this one is a hard plastic shell with a removable 2500mAh battery. When it's needed,…