Would you think measuring general alertness / focus would be a close proxy (or accurate derivative depending on how you frame it) to what you propose?
Assessment can give me that kind of information; hence, my belief that making instruction-based assessment more globally trustable is the key component.
Again, I would love to see something like this come to be. I’d love to jump ship and work on it full time. It would not only provide significant academic advantages, but also make increased teacher compensation politically palatable. If we can measure teacher effectiveness, then we can reward it. If we can’t, we use tenure.