1. A method, comprising: identifying a plurality of feature points from a current video image from a camera; comparing positions of feature points from the current video image with corresponding positions of feature points from a prior video image from said camera; determining, from changes in said positions of said feature points, three-dimensional movement of the camera; outputting an identification of the three-dimensional movement of the camera as a gesture output; counting the number of identified feature points in the current video image that were also found in the prior video image; comparing the number of identified feature points with a predetermined minimum number of feature points; and updating the feature points by identifying one or more new feature points in the current video image if the number of identified feature points falls below the predetermined minimum number of feature points.