This post is about the android app. How do you define "online" when you're on a phone with a data connection, an extremely common use case for this scenario? (Or rather, what makes someone "offline" here?)

Maybe it's better to track whether the user is busy or free-to-interrupt, which I think is what Google is already doing. (I believe there is also an option to broadcast if you're on your phone or your desktop, although I don't fully understand why it's that useful)

Edit: I looked up Google's documentation, and apparently they do indeed track Online/Offline in the hangouts app [1], but from what I understand, installing the android app with a data connection = online. I'm not sure what Offline means.

I guess the parent is asking for notifications about the Online/Offline change, which does not exist. (But again, if installing the app means you're always Online in hangouts, you won't get any notifications anyway)

[1] https://support.google.com/hangouts/answer/3111918?hl=en