There has been a model out for a long time which requires the shooter to have a special ring before it will fire.
I can’t recall the model but the whole idea is just plain a bad idea for many reasons.
Now that I think about it, the gun which requires a ring to fire is a modification rather than an entire gun. Maybe just S&W revolvers but I am not sure.
“...requires the shooter to have a special ring...”
I wants my precious, I does.
The pistol in question was a prototype double stack 9mm built as a technology demonstrator by Colt. I don't remember if it actually functioned or not, but I would never bet my life on it working in the gravest extreme. If you want to see how well these “smart” guns are received, inflict them on your local and state cops — if you dare.