Gunshot detection does this, but raises privacy issues: https://en.wikipedia.org/wiki/Gunfire_locator https://en.wikipedia.org/wiki/Gunfire_locator You end up

Gunshot detection does this, but raises privacy issues: https://en.wikipedia.org/wiki/Gunfire_locator https://en.wikipedia.org/wiki/Gunfire_locator You end up with a city-wide monitoring network that can be misused.