This image posted by perpetual juicy rumour machine @evleaks shows what could be a forthcoming iPhone gaming controller from Logitech. Given Apple's reference designs for such a controller released at WWDC this year, the supposed leak looks pretty legit.
Indeed, the purportedly forthcoming controller looks pretty much identical to one of the two designs that Apple released in the iOS 7 documentation over the winter.
The tweeted image looks like your standard SNES controller: Four-way directional pad on the left, ABXY buttons on the right. We can't exactly see what's going on top of the controller, but it appears the left and right shoulder buttons from the spec controller are there as well.
The camera hole on the back is an interesting touch. Presumably, you wouldn't use this forthcoming Logitech device at all times the way you do a case, so it's not exactly clear why you would need a slot for taking photos while gaming. Developers have yet to work the iPhone's camera into many (any?) games. On the other hand, why not?
If this device is real, we'll surely have answers to all of these questions soon enough. Now the waiting game. Back to my boring touch-based Infinity Blade.