I've been contemplating doing a Firefox Extension as a personal enrichment technology project (obviously extensions aren't a potential revenue market), and have played around with the rudiments: Tremendously powerful, and very easy to take each step, and while there are specifics that I haven't nailed down, most of the enabling functionality for the following requirements seems to be there.

Before I waste the time I thought I'd put a general query to see if anyone has seen anything like this (searches yield nothing that looks similar).

• Record and report the time spent on all sites, or selected sites (e.g. defined by regex patterns, or groups of regex patterns), allowing for various reporting levels. e.g. domain, subdomain, folder, document, etc. Reporting could be facilitated via the new SVG or canvas functionality.
• Based upon the recorded time, allow the user to "ration" their own access. e.g. "Limit me to 20 minutes of Slashdot per day" or "Limit me to 60 minutes of Reddit, Digg, Slashdot, and JoelOnSoftware per week".

Like most software developers, I peruse the various technology sites during the day, and in the interest of good time management, not to mention that such a tool could be useful for billing purposes, I want to have an accurate grasp of exactly how much time I spend at specific sites, or a group of sites for that matter. Apart from status bar indicators of the time spent, and perhaps time "remaining", the product could be more interesting if it actively blocked further access to that site until you indicated moral weakness and selected the override feature.

Come across anything like this?