well, I don't know squat about lasers (except i don't think I can get one at radioshack), but I do know that speed of sound depends on altitude (T), so corrections would have to be made when using sonar as well. I believe this is true for ultrasonics as well (I am assuming you are talking about looking at the phase shift with an emitter/detector pair in combo with the dopplar effect) . This implies that the use of sound and ultrasound cannot measure TAS, although I have seen these type of airspeed sensors.