I'm not making this a suggestion because it may not be something a lot of admins would want.
In Admin Controls on a member's profile page it would be great to see how much time the member has actually spent on the site. I don't see anywhere on the database where this info can be extracted, but Anton has a module that allows the activity time for the entire site to be shown in the Stats.
My questions are:
Can this information be extracted on a per member basis or does it require code to initially save the data?
If the information is there, can you supply a SQL query to extract it?