iOS 7 (2013) introduced the GameController framework, an SDK to allow game developers to detect physical button presses / D-pad, etc...

This was designed to work in conjunction with hardware makers who made game controller shells that housed iPhone / iPod Touch, but with some extra physical buttons.

I always viewed this as laying the groundwork for an Apple TV App Store, but it seemed to instantly lose traction and haven't heard anything about since the couple of months following WWDC 2013.

I assume that API will gain some more steam now.