Wish I had an answer for ya. I am researching the same thing for a 2-zone with cooling as well as heat.

Honeywell has WiFi enabled thermostats that start under $90 and I presume that their app will notify you if the temperature falls below a set point. If you don't need it to "learn" or do anything else fancy, frankly I'd start there.

One thing to think about is that more often heating problems are related to a power outage, not a mechanical failure. If you loose power at the cabin, you're also likely to loose internet connectivity.

All, thanks so much for your contributions to this thread. We decided that "smart" thermostats were overkill at the moment so we're getting Lux programmable ones (still overkill but when we live there FT we will appreciate them). For temperature monitoring I'm looking at the Neatmo monitor -- if others have suggestions, please recommend.

I have no experience but the ones at wirelesstag.net - they look excellent and I'm thinking of ordering. But they basically assume you have internet/ethernet (or wirelss that can give you internet). I know about the issue of power out - in my case it works because if power and ethernet are out, I will at least know that and can have a neighbour check. They also have modules for water and movement (so basic alarm functionality), etc.