How often would you like to know when your friends are with you? Or, for example, your friend went on vacation, and you know about it only on his return - a shame, yes? Now, with Google Latitude Alerts, you'll always be in the know if your friends walk past you on a nearby street or if they’ve found a friend in South Africa - but they didn’t tell you about it.
Turn on notifications for friends on Google Latitude and select the confirmation option by email and / or SMS. And do not ask each other more by phone "Where are you?"