Simmer down in the streets of Groningen

Apparently technology now exists to tell if people are talking in an aggressive way. Wired News is reporting that the city of Groningen is doing a pilot project that involves installing microphones in the streets to detect if people are yelling angrily so that cops can be summoned. See: Listening Post. I guess you'd have all problems solved if you combine this with a gunshot detector (The Canadian Privacy Law Blog: Surveillance technology cleans up the streets of NJ town) and a tweak to catch conspiratorial whispering.