Telepathy is a communications framework built around DBus. Connections to IM servers, text conversations, and voice calls (for instance) can be implemented with a number of separate processes, interacting via the session bus. This approach allows each component to do one thing well, rather than requiring a single monolithic application to provide every piece of functionality. It also allows any new UI to reuse the existing connection managers rather than having to reimplement every protocol itself.
Telepathy protocol plug-in
libpurple-based connection manager
Will Thompson started telepathy-haze — a Telepathy connection manager based on libpurple — for Summer of Code 2007, mentored by Robert McQueen. (His project proposal also originally included writing a Telepathy prpl, but there wasn't time.)