I have a Honeywell RWD41 standalone water alarm - it looks like this:
The reason I like it is that there is a four foot sensing cable - if water is detected anywhere along that cable, it goes off. Its great for looping around the base of a hot water tank, or I use it on the perimeter of my washer machine and refrigerator.
Is anyone aware of a 2gig compatible sensor that is similar? I haven’t found such a sensor for any alarm system, but its super useful.