Microsoft has patented a type of dual controller that is both wired and wireless.
There are pros and cons to wired and wireless controllers. With the former, you know you're not going to run out of battery mid-game, but you can't really go very far. A wireless controller allows for a lot more movement, but you might find yourself low on controller juice at a pivotal part of the game.
A patent filed by Microsoft with the U.S. Patent and Trademark Office earlier this year attempts to solve this dilemma by being both wireless and wired. By the sounds of things, you'll be able to switch while you're playing and the controller would be able to inform currently played game to flip between the two. SlashGear reports that the game wouldn't need to be paused, and it could automatically keep track of which controller goes with which player (and their accompanying saved games).