My biggest concern is that it is not effective in reducing gun deaths- the vast majority of deaths are caused by the rightful owner of the gun. This hypothetical technology would not stop any of those.
I'm not sure where you're getting that information. Roughly speaking, there are 40k gun deaths/year in the US. 75% of those are suicide, and of the remaining 10k, the vast majority (I think 85% is the number I heard) are gang-related. "Smart gun" technology is designed to address a particular situation--an unauthorized person (say, a kid who found a gun, or someone with a stolen firearm) is trying to pull the trigger--and won't actually have any affect on the vast, vast majority of gun deaths. Granted, some firearms used by criminals are stolen, but it's still not a huge percentage of cases.
I have a good friend (actually a friend of my husband's) who has a carry permit and carries all the time. He's a very nice guy, but a tiny bit of a nut. Also, he has a palsy and though he used to be quite a good shot, his aim has deteriorated considerably over the years. If this person was a teacher in my child's school and the administrators of this school had actively agreed with this teacher that he was going to be a conceal carry teacher in the service of protecting the children, I would want to know. Because this guy's aim could actively endanger my kid in the event of an active shooter in the school.
If there's an active shooter in the school, and your friend has to shoot at the bad guy in order to prevent the bad guy from killing a bunch of kids, I'm not quite sure how his aim would actually make the situation worse. I don't mean to sound callous here, but the worst-case scenario is that he kills or injures someone the bad guy was going to kill anyway.
Japan seems to have done so. It would not work with our Constitution but it is possible.
True, but it's an anecdote. The UK has done the same with gun ownership, and yet they have some major crime issues. I believe it's important to look beyond "guns are used to do bad things, therefore we need to get rid of guns," and address the root cause of crime and violence. In the US, a large majority of the gun-related crime (setting aside suicide for the moment) is associated with gang activity. If we can address the gang problem, much of the crime problem goes away.