Fact: My iPhone 4 has crummy battery life. Fact 2: The iPhone 4 does not have a removable battery. Fact 3: Sucks. The Third Rail aims to fix this: It's a slim case that lets you tack extra batteries on.
The "mobility system" is a case and an extra 1,250 milliamp battery, which'll juice your phone's battery up by an extra 70-percent. And if that's not enough, you can add more. Dope! I only have two, but nothing I have read or can think of would prevent you from stacking on, like, 200 of the little suckers, making a literal tower of power that would electrify your iphone for the next few months. You could go totally off-grid. You could find a cave and play Frog Minutes on your 4-foot-thick iPhone long enough to figure out if there's actually some larger purpose to catching all those digital grasshoppers. Sounds reasonable.
Or you could use the extra cells to charge the other gadgets you'd need for cave life—bluetooth headsets, cameras, iPods, anything that has an affinity for a 5-volt stream. Each so-called "smart battery" has a USB-out jack.
Oh, and if 200 extra batteries seems like overkill to you (pussy), consider the picture above: two batteries add the perfect amount of extra booty to your iPhone to make it stand up on its own. It's like a kickstand full of electricity.
So, remember when I said we should get like 200 of these and have a party? You're gonna have to pay—this stuff ain't cheap! The system, which includes the case and one battery, is 90 bucks. Want another battery? Get ready to shell out another $60.
And unless you're wearing hammerpants, you aren't throwing a bodaciously battery-bedecked iPhone in your pocket. Each cell is a quarter-inch-thick. You might be able to slide the phone-plus-one into your skinny jeans, but any more than that is a bit girthy—especially considering that the extra bulk sticks out in a weirdly shaped electro-tumor.