From the Google Pixel 4a announcement:

Pixel 4a also has Live Caption, which provides real-time captioning (English only) for your video and audio content. New with the Pixel 4a launch—and also rolling out for Pixel 2, 3, 3a and 4 phones—Live Caption will now automatically caption your voice and video calls.

Follow the headline link to watch The Verge’s Dieter Bohn demo this. I’d love to see Apple add a feature like this to iOS and FaceTime. It’d be great for accessibility, in the same way as closed captioning provides an assist when you are watching a movie.