Apple has won a US patent on an accessory that adds tactile buttons to the display of a multi-touch device. AppleInsider
notes that the accessory
would use suction to stick to a screen, and feature buttons that deform and spring back as they're pushed. To actually register touch input, tiny rubber or metal pucks might be embedded into the buttons. Some buttons could be used as finger rests, and Apple also suggests that the patent could be applied to a joystick.
The patent is unlikely to see use in a shipping Apple product. An application was first submitted in 2008, and the company has never sold any accessory of the sort. Third-party gear makers have also created their own overlays, such as game controllers and keyboards, reducing incentive for Apple to do its own work.