I played with a demo model at the NRA convention and was favorably impressed.
It monitors the movement of the gun and when it detects the gun being fired/dryfired, it records the movement for a short time before the shot and displays it. This makes any flinching or trigger technique problems very obvious.
Here's a short blurb I wrote up after the demo.
https://www.thehighroad.org/index.ph...dallas.836429/