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.