XMPP is a feature-full (despite what those who haven't tried it will tell you) federated instant messaging IETF-standard protocol. Which so happens to be perfectly-suited to the web-centric foundations of our hypothetical hardware-Internet Communicator! Though with little extra effort I'm sure you can apply the same techniques to SIP, Matrix, the cellular network, or whatever; this is left as an exercise for the reader!
I'll be exploring the basic Core, IM, & A/V Calling XMPP profiles.
1/3?