So, initial impression, it's Kinda Cool. Going with what I have en masse, months and months of podcasts, that's what I tested with. I notice that people on the podcasts I listen to talk very quickly. And the app struggles to keep up, kind of munges together the different participants in a conversation
Trouble is, deaf people might get no useful content from this at all. Somewhat hearing impaired folks, and I am a bit, would mostly need the help with the harder words and proper names and those are exactly what the app misses.
So it's a clever toy, and yet another maybe-someday-it'll-be-useful gadget. Feel free to play with it, but don't bet your life or livelihood on its accuracy.