No matter the system, something will go wrong eventually. A power glitch, a disconnected controller, or a hardware failure. That’s why you need a backup thermostat wired directly to your heater.
If your primary controller fails, the backup takes over and prevents a freeze-out.
Set your backup thermostat 3°F below your main setpoint. This way, it only kicks in when something fails, without interfering with your usual temperature target.