Facebook tracks the country you usually login from and if you login from elsewhere in the world it asked you some security questions. This is tracking location based on IP and seeing remembering where your usually at.
This service could be separated from Facebook and made a stand alone service that any large website could pay to attach to their site.
It could be enhanced to track OpenID login accounts and also made more intelligent if the account owners used something like Google Latitude so their current location could be matched automatically. This might also enhanced banks online security for credit card transactions etc.