[nobody9999]

>'Alarms' are probably useful. A loud 'alarm sound' would definitely have an effect on an intruder, they often alert some authority if left on, and cameras start recording.

>I find them extremely common in the hyper-safe suburbs where every kid is in a safety bubble, probably the lowest crime areas going. They're sold for inflated prices.

Alarms are definitely useful. Mostly because in many places, having an alarm system installed will lower your homeowner's insurance premium.

As long as the ROI is less than how long you intend to live in that residence, it makes lots of sense.

Beyond that? Not much value.