With Google Latitude, you can share the location where you are. Google Latitude gets a new facility now though which you can connect that location to a real place.

You can still use Latitude to share your location but check-ins lets you to add some text to your location.

See the below image illustrating Check In with Google Latitude.

Google has added few twists to make checking-in easy:
* Notifications
* Check out
* Automatic check-in

Check-In with Google Latitude

Google Latitude App for iPhone

You can start check-in by downloading latest Google Maps from Android Market.
For iPhone, join Latitude from main menu. If you are using new Latitude app for iPhone, you will see your friend’s check-ins and google will update the app soon, so that you can also check-in too.
Download Google Maps for Android.

Download Google Latitude from App Store.