Normally I just set the thermostat to 55, shut off the water, and leave. But last year my furnace packed up shortly after I returned -- control board had to be replaced. It could have been a problem if that had happened while I was gone.
So this year I'm putting in a temperature alert. I decided on the simplest, rather than a web-based one. Nothing to set or adjust. It will call me if the temp drops to 45. Then I can get my neighbor to go in, and call the HVAC folks.
I'd rather not rely on the functioning of my broadband/router to get this done.