Google have added some new features to its location tracking service Google Latitude:
Google Location History
Using Latitude you can keep track of your location history. You can store your past locations and visualize them on Google Maps and Earth. Enabling location history means that anyone can produce their own road trip or travel map at the click of a button with Google Latitude.
Google Location Alerts
If you enable alerts in Latitude you can get notifications when your friends (who use Latitude) are nearby. Location History also allows alerts to only trigger when you are in an unusual place, filtering out routine alerts. Alerts can also notify friends where you usually are on that day and time to explain why your location is unusual and the alert was sent.
Via: Google LatLong