People buy guns primarily for home defence but they often end up being discharged accidentally and injuring the owner’s own family members.
There is also the danger that a burglar, confronted by a firearm, might get control of the weapon and shoot his way out.
Today’s invention is to fit domestic firearms with a small camera running face recognition software. This is now actually very reliable when asked to find the faces of only a small number of individuals.
It would therefore be trained to detect all one’s family members and used to control the safety catch on one’s home gun.
If this device was pointed at any of the designated people, then the safety would remain firmly on, avoiding some possible tragic consequences.
Would the safety be on if a face is not detected? If so, then it would be useless in self-defense against a masked attacker. If not, then a stolen weapon could still be fired simply by covering the camera, or firing at the owner when his or her face is not visible.
Instead of facial recognition, I would suggest trying RFIDs for this sort of system.
The idea was that the gun would fire normally, unless one of a small number of faces was detected. All sorts of possible problems could occur if a family member was wearing a halloween mask, for example, or turned their back, but a masked attacker would be as vulnerable as usual.
I like your idea of having family members each wear an RFID dogtag (somewhere beneath their clothing), but you’d have to make it compulsory, which as anyone with a family knows, is difficult. Maybe it could be incorporated into a small earring which was never removed (which would work better in some families than others!)