A method is described for determining a description of motion of a moving mobile camera to determine a user input to an application. The method may involve capturing a series of images from a moving mobile camera and comparing stationary features present in the series of images. Optical flow analysis...http://www.google.com.tw/patents/US7379566?utm_source=gb-gplus-share專利 US7379566 - Optical flow based tilt sensor
