There was at least one company selling this sort of thing as a product back then. It was more efficient than conventional electric heating, if I'm not mistaken, even without the income from mining.

Move into a cold climate, and buy a house that has only electric heaters. Those were popular in the 70s, and nobody wants them now, so you can buy one with pocket change. Build a mining cluster in one bedroom and install air ducts to distribute the warm air throughout the rest of the house.

There's a space heater called the Trio and a few furnace replacement things. And in general, waste server heat can often directly plug into central heating systems, be it mining bitcoins or Google datacenters.

It's not the snooping, it's companies making their own incompatible proprietary system and jealously guarding it to force you to only buy their stuff, except everybody else is doing the same thing so the actual result is that getting things working together and keeping it all working is a pain in the ass.

We're still talking about marginal, unnecessary things, but with a "smart" coffee pot, you could in theory start the pot when you're a few minutes away from home, if you like some after work. A pot connected to something like home assistant (which I have no idea if it exists) can brew the pot only on your workdays, or you can start it after you leave the bedroom, regardless of time. You could probably do quite a few "neat" things.