Perhaps in relation to this patent (and a host of others, I'm sure)...
METHOD FOR CREATING A PEER-TO-PEER IMMEDIATE MESSAGING SOLUTION WITHOUT USING AN INSTANT MESSAGING SERVER
METHOD FOR CREATING A PEER-TO-PEER IMMEDIATE MESSAGING SOLUTION WITHOUT USING AN INSTANT MESSAGING SERVER
I hope they lose the case and their patent is invalidated. (Isn’t this system highly similar to how Napster messaging and AIM “direct connection” chats worked, before 2004?)
Anyway, here’s another US patent that could be relevant. Seems even weaker, though: “A method of displaying messages on handheld devices. The device displays messages in a scrollable viewport of vertically arranged fields. Date separators inserted into the vertically arranged list of messages to enable the user to associate the messages with a date. …”
4G cellular networks are all IP and use SIP for signalling. I doubt phones are publicly addresssable though, the telco probably NATs them.
I eagerly await a number-free, VoIP-enabled, IPv6 world.