I've noticed a need for this both as a mortal and as a mod. If I could set up a list of "people to watch" that would show me the same information as the currently active users list except with only those people, that would be stellar! :)
On a related note, I'd love to be able to view the currently active users list specific to a single forum or category as well. Rather than seeing every member and his brother along with every guest and his extended family, if I could just view who's actively working in the forums of my choice, that would be wonderful. I've always wondered why the individual forums show currently active users but don't let you get the specifics like the global user list. It seems kind of inconsistent.
I know you don't have enough work Dani, so here's my contribution. ;)