A mobile electronic device with a virtual input device. The virtual input device includes an optical sensor for detecting movement of a user's fingers over a work surface and an acoustic or vibration sensor, for detecting an impact of the user's fingers on the work surface. A processor, coupled to the optical sensor and to the acoustic sensor, processes the detected signals as input for the electronic device. The user's fingers can be shown on the display overlaid by a virtual mask. The virtual mask may show a keyboard of menu items.