Another gimmick. And more money in someone's pocket.
People that show horses who are exposed to carnivals, balloons, and all sorts of odd things, do not spend time trying to despook horse. If horse is being handled right? Rarely is any of this needed.
If it is? You can record all sorts of sounds yourself and save the money.
Same with desensitizing, you can do pretty much the same thing with a rub rag. And get same or better results.
Save your money would be my suggestion.
Horses make me a better person.