This is one way for iPhone users to keep track of buddies. I think its going to be of excellent use on Universities with large campuses. Especially since you want to know where your friend is without disturbing him or her in the lecture.

Using Buddy Beacon, iPhone users can share their location with friends and they can see the locations of their friends on the iPhone's map application. Users can also connect with friends directly through the application and update their status across a variety of online social networking sites, including Facebook.

The software also allows friends to nudge users to update their status and location from within the application.

Use your iPhone and head on to http://www.where.com/bb to get this app

Source