Yeah, you can use the referer library mentioned elsewhere for this same purpose, just add the query function to find last accesses by time. You could also potentially stash the user's ID if they were logged into your site, and with that display names..
On the last point, I actually have significantly updated the refererLib code on my site, including the use of $wpdb specificially to prevent any chance of opening a second connection the to SQL server -- not wanting to count on the mysql fns to do so. I agree with the desire to keep things cross-app-compatible, yet for actual release I'd hate to have a half-dozen connections to my sql server (which isn't the same box at my hosting site as it is on my home test box!)...