Facebook users carrying their smart phones will soon be able to check in to real-life locations such as restaurants, bars or live concerts.It's the first foray by the world's largest online social network into the frenzy of location-based services. Rising with the popularity of smart phones, such services let users find coupons, earn quirky merit badges or simply share with friends where they are.The new feature is called Facebook Places. Sharing your whereabouts with friends is its main focus.Check-ins will be available on Facebook's iPhone application Wednesday with a free update users can download, as well as on the site's touch site used by many other mobile phones. Versions for Android and BlackBerry will be available soon.The application will use GPS so people can "check in" and let friends know what they're doing. The idea is that if a friend sees you are in a bar, cafe or club, they can come to the same place to see you.The service will also identify other popular spots in your area, as well as comments and reviews others have written about the place.