Over the years we have updated the user_tracking.php tool and made a few bug fixes. One feature we added was changing the script into a form and adding a popup date selection menu so you can select a specific date to begin the listing. This has proven invaluable since we actually keep several months worth of logs and it was difficult to page though using the previous page at a time GET method.
In any case, I have not previously read this thread so there could be a newer version out with other features or bug fixes. Perhaps who ever is maintaining the code (Pinghead) these days could merge this version with any fixes and updates previously done and make a new release. For now though, if you want to give the version we use a try, it is available here:
user_tracking.zip.
BTW, this is just the single admin/user_tracking.php file and assumes you already have a working installation.