Back in November 2009, Google launched a new beta service "Location Alerts," -- part of Google Latitude, was launched alongside the Location History feature. "Location Alerts recognize your regular, routine locations and sent you alerts when you're either at an unusual place or at a routine place at an unusual time."
However, Google has quitely killed this service with follwoing message in the support page;
The experimental Location Alerts (beta) app was retired in December, 2010. Retiring features is always a tough decision, but part of building experimental features is picking the best ones on which to focus. Rest assured, we're continuing to develop apps such as Location History as well as the Latitude API to enable the developer community to create even more ways for you to use Latitude.