They’re somewhat useful for monitoring. I don’t expect that they’re much of an actual deterrent and ymmv on if they’re worth the price.
But don’t discount the value in monitoring something that you can’t fully control. By the time someone greats into my house they’ll be long gone with anything of value when the police arrive (if they ever do), but having something alert me and the local Fire Department in case of smoke is useful. Same with leak detection and flooded basements, or break-ins. These are things I’d much rather know when they happen so that I can remediate, gather pets that may be wandering the neighborhood after door kicked in, etc during the day than after getting home from a long day at work (not issue in Covid-19 times). Even worse to come home to find a problem when getting back from business trip or family vacation.
But don’t discount the value in monitoring something that you can’t fully control. By the time someone greats into my house they’ll be long gone with anything of value when the police arrive (if they ever do), but having something alert me and the local Fire Department in case of smoke is useful. Same with leak detection and flooded basements, or break-ins. These are things I’d much rather know when they happen so that I can remediate, gather pets that may be wandering the neighborhood after door kicked in, etc during the day than after getting home from a long day at work (not issue in Covid-19 times). Even worse to come home to find a problem when getting back from business trip or family vacation.