For most of the tests, they used a dedicated ultrasonic speaker. However, they also tested it with a Samsung S6 Edge controlling an Apple watch; it worked. So y

For most of the tests, they used a dedicated ultrasonic speaker. However, they also tested it with a Samsung S6 Edge controlling an Apple watch; it worked. So you don't strictly need specialized hardware. Whether or not it works for TV depends on the broadcast signal (processing, audio codec) and the playback device speaker. The latter should work out somehow, given that a smartphone speaker can do it. Most audio codecs go up to 44 or even 96 kHz, so the range should be there. But digital TV signals carry lossy audio, designed to save space by throwing away data not discernible by humans. I'm not sure how high the fidelity of AAC is beyond 20 kHz. Should be easy enough to find out.