You can cast your device's screen, but you'll still have to rely on the device's camera and mic.

You'll probably want to avoid outputting the sound on the TV or you'll get a feedback loop.

And there's going to be a slight delay, which might be annoying with a realtime conversation.

So it might not be a great idea from the start.

You'll also end up with 15 fps, high CPU usage, and random hangs... It works, but isn't really usable...

Well, with the google home app, you can send your whole screen to a chromecast, so whatever you are doing on your phone will be visible on your TV.