Rosedale, there have been lots of tests of such devices. I remember last year there was a study of this sort of the exact position of each vertabra of Shizuka Arakawa's spine when she does an Ina Bower, because it seemed to be impossible what she could do.
The tech problem lies with the supposed sensors in the blade. What do we mean by the exact moment of take-off and the exact moment of landing?
By the way, the comparison with that instant replay thing in tennis that shows whether a ball is in or out, is interesting in its own right. What we see on our television screens is not the tennis ball. It is a computer-generated cartoon. Many players swear that what is shown on TV is absolutely not what the ball actually did in real life.