There is no decent "fail safe" system for hydronic heating. It's just people following some old convention.
Zone valves can be normally open or normally closed. The normally open valves require constant power to stay closed, the normally closed valves require constant power to stay open. They have a spring return. Really old zone valves were motorized both ways, with a limit switch at each end. They wouldn't help because a closed valve will just stay closed.
Modern buildings and hydronic heating designs use normally open valves because they "fail safe" in theory. If there is an open circuit or loss of power, the valve springs opens for full heat and there is no danger of pipes freezing.
One example is apartment buildings, condos where the suite is unoccupied and has power shut off- the 24VAC zone valve transformer is not energized and you don't want the suite cold, so it defaults to full heat.
No matter what it's a crappy design. Running glycol gets rid of the zone freezing (aside from other plumbing) but there is a big hit in efficiency as glycol is not as good as water.
With hydronic heating, you really need a low temp alarm. Nobody has rolled out a smart zone valve yet.
Note modern googlegarbage thermostat like the Nest does offer
"HVAC monitoring" offered in some regions but it looks like children wrote the software for it.