That would just apply to the Location setting in OCS that no one seems to use. As far as having some custom application to pull GPS data and set the users presence accordingly, there is nothing in place to support that.
You can define up to four different custom presense settings for users, but that requires an XML by placed on each workstation and the OC client must be restarted between changes. But
if you are talking about using data from a phone then your even more limited in options for scripting a Windows Mobile app to do so.
The upcoming R2 release will have a new presence setting for showing when users at logged in via Communicator Mobile versus the workstation client, but not to the level of detail you are asking.