Who knows, maybe the seat "is" actually using mining to heat the seats. That would be quite the April fools joke.

Every resistive heating device, be it hot water system; space heater; kettle; oven; stove; heat lamp; etc, could just be a proof-of-work IoT device that generates (very little) income.

If everything did that, the profit from doing it would be almost nothing, as difficulty increased. It would also be wildly more expensive than just a simple piece of nichrome wire, and you also now have to have a cellular module and a significant amount of continuous data traffic over it.

Yes, but people would make money in the gradient in between when nothing does it, and when everything does it.