I successfully implemented a system to notify me and shut off the water main to our house in the event of a water leak. I used four Smartthings GP-U999SJVLCDA water leak sensors at various places in the house (bathrooms, kitchen, laundry). And I used the DOME DMWV1 Home Automation Water Shut-Off Valve.
After setting up the water leak sensors and attaching the Dome unit to the water main shutoff valve, I set up a Rule Machine action. It simply notifies me by SMS, then commands the Dome unit to shut off the water. It works great, and I recommend it to any homeowner. Water leaks (e.g. from toilets, washing machines, sinks, burst pipes, dishwashers, etc.) can cause massive damage to a house.
The only thing that won't be shut off is the fire sprinkler system. I installed the Dome shutoff unit on the water system just beyond where the fire sprinkler pipe forks off from the water main. There is a water shutoff valve that only shuts off the non-fire-sprinkler plumbing for the house - which is where I attached the Dome unit.
I also set up an IFTTT rule using an IFTTT service called "Call me when Hubitat device detects water". For some reason, the service didn't actually call me until four hours after the event when I tested a water leak being triggered. The IFTTT log indicates that the service triggered at the exact time when I ran the test. But the phone call didn't arrive for four hours!
And finally, I want to modify the notification process to send me an email when a water leak occurs (in case I'm out of town when the problem occurs). Unfortunately I haven't yet found a way to send an email notification from Hubitat. Might have to write my own app to do that.
