An image of the alleged Logitech MFI mobile game controller has been leaked on evleaks Twitter account. The iPhone depicted in the image, appears to be the iPhone 5; hence, the latest iPhone 5S will fit into the game controller.
The Logitech MFI device has a D-pad on the left, and a simple four-button layout on the right. It also has two left and right shoulder buttons, with a rear opening for the iPhone's camera and flash. However, this may not be the final version of the device. As Apple Insider has noted, it isn't certain if the game controller will be compatible with the iPhone 5C. Other iPhone models will definitely require an adapter.
According to MacRumors, since the release of iOS 7, a number of game titles have incorporated game controller support. This Logitech device will have some appeal to hardcore iPhone gamers. This leak also suggests the possibility of more such devices on the horizon, so do stay tuned for more developments. For more information on game controller support of iOS 7, do head over to the Apple developers' site here.