A low number of false positives with a water pistol is an impressive engineering feat. A low number of false positives with an actual gun is a disaster. The technology is still a long way off.
Accurate sensing, the ability to accurately distinguish between combatants[1] and non-combatants, seems to be an almost impossible task. While there are robots in active service today they all have a human involved somewhere, especially if there's lethal force going to be used.
It's pretty scary to think that humans could be removed from that loop. I can't work out why I'm happy to see totally autonomous cars but I'm wary about autonomous weapons.
[1] And even if you can identify an enemy combatant you've got to then distinguish active combatants from those who have surrendered or are injured or are mentally ill.
