I'm guessing this won't work for the "cast" button from my computer or from apps or websites on my phone like Youtube, Vimeo or All Four (the uk channel 4 app).

I'm guessing this won't work for the "cast" button from my computer or from apps or websites on my phone like Youtube, Vimeo or All Four (the uk channel 4 app). I like what they've done, but Google has really locked this down unfortunately.