By monitoring any area more, you find more crime, which results in that area being considered as "high crime" and in turn increasing monitoring--that's the cycle OP is talking about.
The devices monitor specifically for gunshots. I find it hard to believe that gunshots in wealthy area's often go undetected, with or without those devices.
First of all, unless you’re completely overwhelmed and not even bothering to enforce certain laws, you’re going to find out about most of the serious crime that takes place. Law enforcement is made aware of homicides either through missing persons reports or the discovery of dead bodies. Armed robberies and grand theft are usually reported if, for no other reason, than to create a paper trail for insurance claims. People who get shot or stabbed badly enough to end up in a hospital, end up in a hospital so there’s a reporting mechanism there. It’s not normal for most major crimes to happen completely outside of the attention of law enforcement unless things have gone very very wrong (which admittedly they have in many American cities). And much of the time, you can infer where these crimes happened.
The benefit of increasing patrols and surveillance in a specific area is more about gathering evidence to solve crimes, and less about discovering those crimes to begin with. In some cases you might end up discovering more crime (especially when gangs are involved and people are intimidated into not reporting crimes) but if you monitor areas where any serious crime would already get reported in the first place, you won’t actually find more serious crime there.
