Mr. Pitot's tube(s)
One or more Pitot tubes have been fitted to most aircraft that have ever flownn and a better system of finding one's airspeed has yet to become general aviation practice - or even perhaps, invented.
This, basically, for those who find to their horror, that all aircraft, ancient of modern, have a "single point of failure".
Mr. Pitot's invention has served aviation well, worldwide, and throughout the ages, so calm down people ... !!