From one new homeowner to another, let me just say ... don't skip this one.
I had no idea water was such a pain in the you-know-what until I was responsible for my very own house. It's very hard to detect a water leak until it is right in front of your face — and at that point you might be dealing with rot, mold, and general yuck.
For example, when my sewer line backed up, there was a waterfall in my crawlspace. I didn't notice right away because I'm not in the habit of going under there. And it was a surprisingly quiet waterfall.
Water leak sensors tell you there's a problem before it gets out of hand. Put them in areas where you hardly ever look: under the tub, sink, garbage disposal, washing machine, and dishwasher; in the crawl space under major plumbing and sewer lines; near the drains in your basement; and literally anywhere else you could possibly imagine water dripping or collecting.