Great data for getting your insurance rates raised.
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!
If companies do start charging different amounts based on smart device data, it will most likely be discounts from an increased premium (which you wouldn't get without smart devices) rather than increases in fees due to usage behavior.
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.