Funnily enough in one of the article's citations, the UK's government has funded SIGINT research for CRT and LCD televisions[0] to see if you're watching the BBC on the flat panel television inside your own home. I've been cold-called by cable companies while in college trying to sell me a cable subscription, and were absolutely baffled when telling them I didn't own a television.

[0] https://www.cl.cam.ac.uk/~mgk25/temc2013-tv.pdf