Google Latitude is a free useful tool that works from cell phones and GPS laptops, its much appropriate site tracking service. If you have a Google Account, you can get started simply by adding Latitude to your iGoogle page on the Web.

You can also browse to google.com/latitude on your smart phone and download the latest version of the Google Mobile app, that contains built in Latitude function.You can also track your friends who are using the service. You just login and get started if you have downloaded it on your cell phone.