Plus, if your batteries run out, then you wouldn't be able to change the temperature anyway. You have far bigger problems than the device being online only.

I believe that's how Apple does it. The local host device is either an AppleTV, or an iPad.

All it takes is for Snake Farm to pay to find out how many times your smoke detector goes off. Or even if it doesn't fully go off, how often it senses anything.

With your thermostat data, it's possible to build a profile of when you're home and away. Hmmm... he seems to work an overnight shift. Better jack up his premium!

So in your case, better buy that smart device.

Companies already do: https://www.progressive.com/auto/discounts/snapshot/

In this case, Progressive gives you a discount in exchange for monitoring you.

But I've seen articles where other insurance companies (often in the UK for some reason) raise rates for things as seemingly innocuous as posting the wrong thing, or being "friends" with the wrong people on social media.