Well, there are lots of alternatives. +/- 0.2 mph is about 0.1 m/s which is often good enough. The Aerostick uses differential pressure sensors so it can tell airspeed and yaw angle within a degree or so, but there are other ways to do it. One of the problems is getting the sensors out far enough away from the bike/cyclist so that you don't get "bow wave" effects. You can do that by by going out in front, or up above, or out to the side of the bike/cyclist, but for the Aerostick we went out front to minimize drag contribution from the sensor itself. But if you don't need this kind of precision you can go much simpler.