As a matter of fact Latitude gained 1 million users in the last 6 weeks, a clear consequence of its launch on the iPhone (read here).
The check in feature offered by Google leverages the fact that Latitude is 24/7 tracking service. Therefore Google has implemented “Notifications” that send you a reminder to check in once you arrived at a place. The software also allows you to automatically check in at specific places you designate. Last but not least, once you leave, Latitude knows to automatically check you out of places so friends aren’t left guessing if you’re still there.
It would not be surprising to see in the near future discounts coming up through check in as Facebook does with “Deals”, a service just introduced in Europe and Canada (read here). The race is heating up between the web giants to take their share of the local advertising business - BIA/Kelsey's 2010 U.S. Local Media Forecast predicts that local advertising revenues will exceed $2 billion by 2014.
Watch below a demonstration video from Google: