A ball control on a touch screen (using a Microchip microcontroller) was realized in a laboratory in Italy. A steel ball was kept at the center of a metallic plate using FLEX board at the Retis lab of Scuola Superiore Sant'Anna. You just need a steel ball, a FLEX board (an embedded board which can be used by all the developers who want to fully exploit the potential of the latest Microchip micro-controllers: the dsPIC DSC family - see the Datasheet), two servomotors and a touch screen.