I don't know, some gifs from different angles would sure have helped more given our lack of devices (though yes, the video does show one important angle).
At any rate the complaints aren't so much in the description but in it being yet another simple trick, of which we see thousands and few if any pan out especially to the level claimed here.
The device was a galvanic skin response device that looked like a mouse.
You put your fingers on it and it would make a tone that would decrease in pitch with less muscle tension. I laid down and tried to decrease the tone and I gradually learned where I was holding tension and how to relax. As the tone got deeper I would get closer and closer to falling asleep.
search for GSR biofeedback on amazon (not affiliated in any way)
There are a lot of surprising skills that we could learn if we just knew how and put in the effort. See e.g. the blind mountainbikers using echolocation to 'see' the path, or method of loci/other memory techniques.