Try "clown nose" as a search parameter. That should give use an idea of what the shooting community thinks of it. It's meant as a less than lethal alternative
First you have to draw your gun to install the device - when there is arguably not a lethal threat presented. That is going to be part of your defense. If the other person then takes presentation of a gun as the first move and then pulls his out to shoot, who's in the wrong? What will witnesses see?
Even if nothing immediately happens, it presupposes that you can attach the device while the other person stands idly by and does nothing. Well, did you not pull out a gun in response to some level of hostility? There's no reason for anyone to just stand there and wait for you.
It's another answer to a problem that isn't addressed. How did the confrontation get off to a running start to begin with? Somebody - you or him - decided to stand their ground, whether for ego or rights is left for an LEO and his discretion or a court to determine. Not having the confrontation in the first place should have been the preferred course of action.
Plenty can come up with all sorts of artificial scenarios to structure the circumstances toward the use of such a device, but the reality is that armed confrontation is a lot more haphazard and usually involves both parties accepting a high level of risk to even be in close proximity for the confrontation. Nobody likes talking common sense on the internet, tho, what they prefer is the usual "What do you do when you wake up to a knife at your throat!?!" It ignores the dog barking or them hammering down the door.
Same here, you have to ignore a lot of stuff to even get to the point where you would need it, and once you draw your gun it's changing the rules of the confrontation to lethal force even if none was presented.
Bad answer. But it does show that people dream this stuff up because it sells, not because you need it. And that's what 'Murica! is all about.