The high-voltage third rail that runs next to a set of train tracks is, of course, something to be avoided. The Third Rail System for the iPhone 4, however, is to be welcomed.
This friendly breed of Third Rail combines a skin-tight phone case and a surprisingly light battery pack you attach to your phone when you need a recharge.
This is actually pretty cool, but i need it for the older model iphone.
so its basically a spare battery for a phone that doesnt let you take out the battery. meh its alright tho