An iPhone-sized computer that can wirelessly connect to a monitor and keyboard could itself act as a mouse (with gesture recognition like Apple's Magic Mouse), a touchpad, a chorded keyboard, or any other peripheral that can be emulated with a touchscreen and some hardware buttons on the side. (Volume up/down could act like back/forward on a mouse, for instance.) This would be great for accessing your own data and applications from anywhere, without relying on cloud storage.