I believe that system is called ShotSpotter. There are a couple drawbacks (coverage isn't perfect), and I've heard someone claim that it is nearing nanny-state

I believe that system is called ShotSpotter. There are a couple drawbacks (coverage isn't perfect), and I've heard someone claim that it is nearing nanny-state levels of surveillance. I don't think the microphones are clear enough to get much more than a blur of noise, but I'm not sure.