When I’m online I’m mostly either at home or at work, and then I’m almost always logged in to my Jabber server. Also, I use different resources home and work. A Jabber bot (or client plugin) which associates resources with geographical co-ordinates could be used to update a central server with your current location (maybe Norm Walsh’s WITW or out to an RDF or KML file). In fact, you could use the API to WITW and Leigh Dodd’s WITW->Google maps translator directly. That sounds remarkably simple. There’s even already a command line tool to update WITW via XMPP!