In a patent filed on March 30th, but publicly released today, Apple has detailed plans on using a pre-existing game controller to control iOS functonailty. The patent, which can be viewed in full, seems to suggest that a game controller would pair wirelessly with an iPhone, iMac, Apple TV, or a similar Apple device.
The patent seems to mainly relate to the method the Apple device would pair to the device itself. Bluetooth would seemingly make the most sense, as the controller pictured seems to be a Dualshock 3.
Maybe now we can play console ports on iOS correctly. Or, you know, just play the game on the console itself.
UPDATE: While many outlets are reporting that the patent is for an Apple Game Controller, the patent clearly lays out plans for using existing remote controls (including game controllers) and NOT an Apple-designed gamepad.