We are still pretty low tech for monitoring home systems. I have a camera from my PC pointed to a thermometer. I can remote into my PC using my phone or iPad and check the temperature. Since I do not have a light over the thermometer I can only do this during daylight hours.
We always shut off our water supply at the meter, even in the summer. I realize some of you cannot do that, but for the rest it is an easy solution. Last week we stopped into our local plumber, on another matter, and mentioned our shutting off the water, he agreed it was the best thing to do. Even if our water heater were to leak, the 50 gallons would get to the floor drain, but that would be the end of the leaking.
Consumer Reports did a recent review of the home monitoring systems; they actually like a model from Samsung better than the Nest. You may already know that Nest is owned by Google.