Door Locks controlled by mirrors. If the mirror didn't like what it saw, you wouldn't be allowed out of your house. Please understand, I fully acknowledge none of us are perfect, myself included (I know that comes as a shock.). I think it's obvious we can all make better choices before venturing out amongst civilized folks. My idea would protect us from ourselves. I'm no rocket surgeon, smarter people than me would have to hunker down hard to come up with the technology that would make this pie in the sky dream a reality. Make no mistake though...it would be a culture changing event on par with all that important shit you learned about in Junior High and forgot.
It would certainly prevent tragedies like this: