Less sarcastically... that's kind of the big issue that people forget. The price of bitcoin is approximately the cost it takes to mine it less the cost of capital or so--in other words, you should expect to spend something like 95¢ in electricity to make $1 of bitcoin. Electricity prices aren't consistent across the world, but the notability of bitcoin is such that you have to compete against the lowest-cost places. In order to make a decent amount of money from bitcoin, you have to consume a decent amount of electricity. And that electricity has to be converted into some other form of energy, which usually comes out as heat or (in some cases) RF leakage.
What that means is detecting mining is as simple as noticing who's using all the electricity (trivial, if you're the electric company), or walking down the street with a wide-spectrum RF sensor and IR gun.
When you look at that kind of power draw,