The Zooz ZAC36 Titan clamps onto an existing ball valve and turns it closed over Z-Wave, so the main water supply can shut off on a leak without a plumber.
It fits over the handle of the ball valve already on the main and turns it, so there is no pipe to cut. It works on quarter-turn ball valves from 1/2 to 1 1/4 inch and needs about 3 inches of space on each side of the valve, so check the space around the shutoff before ordering.
It plugs into a wall outlet and also works as a Z-Wave repeater. An optional backup battery keeps it working through a power cut. Newer units also support Z-Wave Long Range, which helps when the main is in a basement far from the hub.
A wired leak probe comes in the box and closes the valve on its own, even if the hub or the network is down. Place it on the floor under the valve and add wireless leak sensors at the water heater, washer and sinks.