The iPhone is a notoriously fragile device. That's where cases come in. However, this case, by a Japanese firm called Marudai, might be the toughest (and most impractical) case ever made. The massive backside is made of a combination of steel and aluminum, which is apparently tough enough to save an iPhone from a.50 caliber bullet. That is, of course, if the round hits the backside 'cause the front is as exposed as a naked iPhone on the subway.