That's a very interesting point, I built my own system, but I don't trust my own handiwork enough, so I went the middle route:
I got a Siemens RDF302 thermostat (which is a dumb thermostat with a Modbus RTU interface for remote control) and then I use a raspberry pi to change the setpoint temperature according to a remote signal or schedule.
The actual decision to turn on/off the boiler however, is still left to a "real" thermostat made by a professional company, and a malfunction of the automated system is likely to result in a failure to change the setpoint, not in infinite heating.
