Global Joins is a simple BungeeCord plugin to show join and leave messages across all of your servers (and in the Bungee console). It will only show the messages whenever a player connects or disconnects, not when they switch servers.
To hide the normal join/leave messages, you'll need a Bukkit plugin on each of the networked servers. (Alternatively, you can use a plugin that will change these messages to show the joins and leaves for each server in your network as well.)
- BungeeCord build 466+
- BungeeYAML