Shotspotter has worked at least once in NYC, leading to the arrest of the suspected gunman within minutes of being Shotspotted:
At around 4 a.m. on June 7, police responded to a report from ShotSpotter of a single gunshot fired in the Jackson Houses. Responding Officers Luke Paulson and John Carbone went to 325 East 156th Street where the ShotSpotter system recorded the gunfire. At the scene the officers observed a couple in their twenties sitting on a bench by themselves. - Bronx News
Apparently no one was actually shot here; and thus no lives saved or manslaughterers brought to justice, or even lengthy trial/investigative costs avoided, but remember with SS it's the shot that counts!
And that fact that the bullet's trajectory did not actually come in contact with any citizen's body should not make Shotspotter be considered any less praiseworthy than if it had. ;)