A method for a computing device includes determining in a magnetometer, magnetic data in response to a physical perturbation, determining in an accelerometer, acceleration data in response to the physical perturbation, determining with a processor, computed parameters in response to the magnetic data and the acceleration data, wherein the computed parameters includes a first and a second computed parameter, determining with the processor, an initial motion direction indicator in response to a weighted combination of the first computed parameter and the second computed parameter, determining with the processor, a motion direction indicator in response to the initial motion direction indicator, determining with the processor, a function to perform in response to the motion direction indicator, and displaying on a display of the portable computing device with the processor, a graphic image in response to the function.