I believe that if you mine on a TV, that TV has to be running, i.e. keeping the screen on. That would mean a waste of energy and that could make this kind of mining unprofitable.
Or you are thinking on infecting others' TVs to mine for you?
I have the same feeling about these ARM CPUs: they are designed for low amount use, not 24/7, so they may make more heat than hashes. I remember how my older phones did behave as GPS while also charging them. Keep your eyes open and try to not burn down the house.
Of course, I'm also curious on real and proper long-term stats on mining on old phones.
Well, not exactly. One could run the mining device in "headless mode" without ever having to leave the screen turned on 24/7. In terms of graphics processing power, the Nvidia Shield TV packs a punch compared to other Android TVs on the market. My guess is that this "little" device will be able to mine Equihash or Ethash-based cryptocurrencies with ease. The only problem is that there are no mining apps that would take advantage of these GPU-oriented PoW algorithms. So far, I'm only limited with the ARM CPU which is not that very powerful compared to the traditional x86 and x64 CPUs on laptops and desktop PCs. Old phones could be put to good use, although I won't be earning that much with them.
Nonetheless, I think I'll "stick" with dedicated hardware in the meantime to mine cryptocurrencies at home. It would've been nice to do so with a TV, especially at your friend's house, but this is not feasible right now. Maybe in the future, gaming consoles like the PlayStation 5, Xbox One, or the Nintendo Switch will be able to mine cryptocurrencies on TV. If there's demand/interest for something like this, developers will make it a reality. But I guess that there are far more important things to focus, besides this. Just my opinion