Google Talk and Google Voice in Gmail were/are a great voice calling service. Hangouts is still missing a ton of features compared to google talk, although this feature brings back one of them. I still have Hangouts disabled in favor of the old Google Talk interface on my main Gmail account so that I can see a buddy list, see logged in status, and make phone calls.

The gmail stuff is too ephemeral for me. Needs to be an app.

I don't think audio/video goes with email/chat. I think that's there's where Skype might have messed up and ceded mobile to other players.