My alarm implementation covers only the Iro2 functioning properly. In fact, I’ve never gotten an alarm that an Iro2 zone has been continuously ‘on’ for 2 hours or more. (Makes sense.)
I’ve thought for a while about expanding the protection out to a line break that allows water to run forever. My real time processor easily handles this with a flow sensor that has a pulse output. I haven’t put it in (yet) because it’s some amount of work to dig up the appropriate line, cut it, insert the flow sensor, and run the pulse signal output lines to the processor in the house (the rest is easy, including configuring the processor to integrate the pulses to gallons, and to implement an alarm of ‘More Than ‘X’ Gallons So Far Used for a Zone’).
A key design decision is where to insert the flow sensor.
A small (3/4" copper pipe) flow sensor can be used, but it would have to be out at the street, inserted between the meter and the check valve (not a lot of room, and a good amount of distance to run the signal and power wires). No digging required here because the check valve is already in an irrigation control box with a cover.
The alternative is a flow sensor designed for 2" PVC pipe. There are plenty of locations near the house that are usable. Digging required here, and, 2" sized flow sensors are not inexpensive.
An overall consideration for me, noting my Dallas location, is freeze protection for a flow sensor. It doesn’t get cold here often but it does happen (like a few weeks ago when it was in the teens).
My guess is this is a messy enough project (for me) such that I won’t do it until I have a disaster like @tmcgahey did. Then I’ll lament that I didn’t put in the flow sensor earlier.