This is a different suggestion, Brogan.
The suggestion here is to list usernames of people who are currently viewing the thread you're in or the forum/sub-forum you're in. vB, IPB, and phpBB all do this...wouldn't surprise me if all the major forum software providers offer this.
What you're referring to is an indicator on a per user basis as to whether or not they are online - not exactly where they currently are in the forums.