Looks like Peter and the gang at SpatialNetworking have a new release in the works to include facebook and Twitter integration...
In addition to updating the popular Twitter and facebook service, it can also tie in to your Google calendar and import from TripIt and Doplr... cool. The tie in to Google Calendar is very powerful and something that users are going love! See video demo below (source: http://vimeo.com/1313233) - I can't wait for a mobile client!
See also www.spatialnetworking.com
whereyougonnabe July 2008 release overview from Peter Batty on Vimeo.