I've got a wheel choke to angle the back foot into a pinched knee position.
I now use the queen of the hill on the back foot. It'll click if she coils into the back leg properly.
I only watched the first video. Why does he take 15 minutes to say what should take 5 minutes tops. Reminds of kohners pop-o matic game. It might have value. Audio feedback is a powerful tool. I am going to see if I can find Trouble board game in the garage and make a boot leg one.
Here the 'usefulness' of such a tool is described in ~2min.
What are your thoughts on that presentation? Could it be useful with younger hitters? I don't see me buying one, just curious.