If I'm not mistaken, smart TVs can still communicate by via inaudible sound signals directly to other devices. Spooky.
It's terrible though. We really live in a panopticon now.
Any links?
Be careful which apps you allow to use your phone's microphone.
Not exactly the TV manufacturer doing it, but there have been reports of advertisers using ultrasonic pitches to do cross-device tracking.
Slightly different than what gp was talking about but also deals with using invisible audio for DRM