http://gunssavelives.net/gear/smart-guns-have-been-available...
From the article:
"Magna-Trigger conversion is a custom process in which a magnetic piece is placed in the gun, preventing it from firing unless the user is also wearing a magnetic ring. Despite the simplicity in this system, it never really caught on for one simple reason. Generally people want their defensive firearms to be as simple as possible. Simple, well machined firearms make for reliable firearms."
BTW what responsible manufacturer would sell a gun that might not shoot when you need it to? That's a lawsuit-in-waiting for manufacturers. Depending on the local political beliefs, a gun that _would_ shoot under the circumstances is _also_ a lawsuit_in_waiting! So "smart guns" are a lose-lose situation for gun manufacturers.
And when a "smart gun" mechanism fails (say, due to low battery) should it allow _anyone_ to shoot it)? That's what I would want but I think others would want a gun to be disarmed under such circumstances.
Imagine being raped/robbed/killed b/c your gun has a low battery! [the Magna-Trigger system requires no batteries]