1. A method of using a phone that includes a microphone, a 2D optical sensor, and a wireless interface, the wireless interface being capable of transmitting an RF signal conveying information corresponding to audio sensed by said microphone, the method comprising: sensing a pattern in first image data produced by the phone's 2D sensor; sensing said pattern in second image data subsequently produced by said 2D sensor; and determining a movement parameter by reference to the sensed pattern in the first and second image data.