The "rumor" that I heard about 21 was that it was going to be an Internet of Things company for bitcoin mining. So your thermostat suddenly becomes a miner. It doesn't seem feasible (difficulty would go off the chart), but who knows?
The flow of water coming in a home could be converted to electricity to create bitcoins, and the toilet flushings, et al., could be used to create...wait for it...shitcoins.
If one's a farmer, he could capture the methane from his cows via a 24/7 mask, converting that to electricity to runs miners. Imagine what a termite farmer could produce via miniature masks.