I was more under the impression that the gun violence is not really so high as to justify a constant monitoring system to watch out for (especially if you need a person to look over the reports and then alert law enforcement - I get the feeling a emergency hotline can cover this as well).

This looks like it targets a very small (but probably high profile) subsection of criminal activities. For example, it wouldn't detect someone robbing/beating/stabbing someone.

Ah, I might have mistook your surprise for an assumption in the other direction. I agree, I do not think that crime levels justify this sort of expenditure or monitoring. Maybe part of the appeal for law enforcement here is something that emergency hotlines can't replicate: this sort of system allows the police to be virtually omnipresent. An emergency hotline requires an engaged citizenry, one that would call the cops when a shooting happens, something that many pundits would argue crime-ridden communities are lacking.

No problem.

Yes, that might appeal to law enforcement, even if their intentions are good. It would be interesting to compare the benefits to other programs, like raising the amount of patroling police etc.

Oakland police is severely understaffed, by about a half of what a city of this size would require.

Witnesses calling the police can't reliably locate the source of the gunfire. Wind, hills and buildings carry, echo and deflect the source beyond any hope. That's why a triangulating system like this is essential.