As a guy that's been mining for a few years now, I can get behind the idea of mining space heaters. I even wanted to place a small mining farm in the furnace room and then control the vents with individual thermostats to distribute the heat, dumping excess heat as needed.

But mining on a phone, it's just not reasonable. You could put the same chip on a USB stick and it would perform better.

Serious mining makes for some serious heat. If I'm 21 the household heating market is where I would target.