Since you brought it up - personally, I like using the ultra-sonic sensor for tracking. I used one mounted to a stepper motor to track me; setting the operational distance made it nice. All works well unless the moving object and a stationary object (wall) are too close to each other; hence, the perimeter scan will need to have a shortened distance. Once it locks to the target, perform small angle adjustments, left and right, to maintain the strongest reflection and track the best reflection. Once the moving object is outside of the predetermined settings, begin a continuous 360 or 180 scan- depending on your needs.