Well theres statusnet: http://status.net/ http://status.net/ . Which I assume would be trivial to sync using pubsubhubbub or wave-style xmpp extensions. Edit:

Well theres statusnet: http://status.net/ http://status.net/ . Which I assume would be trivial to sync using pubsubhubbub or wave-style xmpp extensions. Edit: wiki says they already support this: "Supports Federation, which provides the ability to subscribe to notices by users on a remote service through the OpenMicroBlogging protocol."