A suggestion that would probably enhance this even more :)

Players can type "/call [Playername]" to call a player. A GUI opens for both players (maybe a hopper gui) with two buttons for hanging up and accepting the call. If a player just closes the gui nothing happens, the call goes on so that they can talk and still do stuff. The gui can be opened again by using "/call" or via using a hotkey. The text at the top of the gui could be something like "[Playername] calling" or "In a call with [Playername]".

A nice addition would be an integration with the plugin CMI to support nicknames ^-^

I hope this will be a feature in the future. Thanks for making this plugin/mod and keep up the great work!

As per #32, this should probably include multi-person calls (aka group chats).