Yes totally possible and very easy Carl Tyler 12.Feb.04 04:37 PM a Web browser Deverloper Toolkits 3.0Windows NT/2000
The thing to remember is that as soon as you enter a place, even with the placecounter you increase the number of people in the place by one. This can be confusing as it may look like there are 5 people in the place, when in fact you just have 5 people looking at the placecounters in your sitemap.
Just have a WritePlaceCounter with the Unique ID of each place you want to watch on a HTML page. Using Domino views for a sitemap, actually makes it really easy to build this dynamically.