Maybe not what you're after, but the Logitech MK850 wireless bundle has three buttons on the keyboard which allow you to swap between 3 computer pairings, which

Maybe not what you're after, but the Logitech MK850 wireless bundle has three buttons on the keyboard which allow you to swap between 3 computer pairings, which is pretty good. The mouse has the swap button on the bottom, which is kind of a bother if you're swapping a lot.