Ideally, a water leak sensor should be used help to catch a slowly failing appliance so you can repair/replace it before it does major damage, not preventing it from doing damage in the first place due to a sudden major leak.
Knowing that this was happening would not have likely saved the bathroom, or the laundry room, but it might have saved the kitchen.
Point is: for water leak scenarios you should think about both clean water coming from inlets as well as clogs in your outlets.. I should get a couple of these to place behind my lowest toilets, where the water came up last time
The leaks that haunt me though... several under the house in the crawl space. Copper pipe pinholes, caused I don't know how much damage (including several ruined water heater elements, maybe even causing the water heater to fail prematurely). Ruined floors. Until they got bad enough that we had no hot water (which was about the time the floor started warping), there doesn't seem to be anyway that we might have noticed. The water bill wasn't unusually high, or maybe it just frog-boiled its way up where we couldn't. There were several more copper pinholes, but they were noticed as muddy places in the crawlspace while fixing the first, or just spidey-sensed. I am also very nearly too fat to crawl under the house, let alone do emergency plumbing while there.
Another incident involved a squirrel. The idiot owners of this house (before us, not the current idiot owners) decided that the easiest place to put new plumbing was in the ceiling (maybe they were too fat too?). Our attic had a new uninvited guest, and apparently PEX piping is very tasty. Or appears that way, the squirrel lost his appetite after biting enough of a hole that there was a leak from above. This leak though, despite the location which should have made it almost instantly obvious, happens almost within 5 minutes of a torrential downpour that lasted better than an hour. That, plus my unwillingness to believe the previous owners had routed plumbing above everyone's heads, meant we didn't get that taken care of quite as quickly as we might have.
My lessons from this, I think, are:
1. We might have caught the crawlspace leaks quickly if there were a humidity sensor (is that how the leak sensors work?) down there, and we could have compared to baseline. That is, if spraying water didn't just fry them immediately.
2. The ceiling leak probably couldn't have been detected very early, given the coincidence with the rain and how it would have raised humidity. Possibly if we had a water pressure sensor, that would have picked it up as a drop, despite there being no faucets running.
Plumbing sucks. Houses build 50 years ago assumed that it could never fail often enough to make it easily accessible. My next house will take into consideration squirrel mitigation concerns.
Much better would simply be digital water meter tracking (which is still amazingly hard to actually do) since when all the taps are off, if you still have substantial water use then you probably have a leak (I would really love a decently accurate ESP-based water meter with like, Sharkbite fittings on it so I could check the water flow out of all my taps or something).
They must be doing it by analyzing the usage data somehow. Maybe they alert when there are too many hourly time intervals that all have almost the same usage (since a leak would be continuous and constant). Or maybe if it has been too long since they've seen an hour with zero usage. Something like that.
Anyway, it should be able to catch leaks anywhere in the house.
Drain pans won't handle a catastrophic failure. I installed this in our house to protect against pipe failure. We had the old grey poly-b pipe (since replaced) that was used in the late 90s.
You can DIY this if you are handy with soldering copper pipes, or get a plumber to install it for a couple hundred bucks.
Apparently water damage claims cost exceeds fire.
[0] https://www.geoarm.com/wv01lfus125-fortrezz-z-wave-automated...