Differences between Bonjour/Avahi/People-Nearby protocols

I recently discovered, through Ubuntu's empathy im client, that exists a protocol that enables the user to talk with anyone on his actual local network. It seems empathy calls this service "People Nearby" and Windows "People Near Me".

After some research I discovered more information: it seems the "protocol" is called Avahi (or Bonjour/Salut(?) by Apple) and permits a user to connect to users, printers and files on the network.

My questions:

1. Bonjour, Avahi, people nearby, people nearby... are these things different names for the same thing, i.e. to connect to "things" (users/printers/files) on the same network? Are these different implementations of Zeroconf?
2. Which IM support this kind of protocol? AIM, Trillian and Empathy support it, am I right? Which of them are usable on a smartphone (Android)? I think Trillian does and WiChat too but only for iOS.
3. Is there an Android app that implements a Bonjour's or Avahi's service for Instant Messaging?