A mobile computing device, including a main body, a processor and associated memory housed within the main body, a display screen housed within the main body and responsive to signals from the processor, an optical sensor fixed to the main body for capturing successive images and providing image signals representative of the captured images to the processor, and a navigation module associated with the processor for determining, based on the image signals, a relative movement between the main body and a reference surface and moving a pointer on the display screen based on the determined relative movement.