Microsoft suggests using structurally separated into two parts, game controller in conjunction with mobile devices. Contact this joystick with a mobile device carried by the wireless interface. This allows for some versatility - you can hook the controller as a smartphone and a tablet.
By the way, the player must help more methods of interaction with a mobile device - Microsoft suggests using gesture recognition using a combination of cameras, voice commands and even to assess brain activity using EEG. Similar attempts were made by OCZ Technology company.