Fliggerty made a Census and Excise Office mod for Morrowind that goes in that direction. It gathers stats about the current game and send it to a website where we can check the characters. I just don't remember if the total play time was among the gathered statistics.
Yeah that's pretty awesome.
It tracks all sorts of cool things indeed. Completed factions/quest lines, level, killed creatures, what kind of spell schools you've cast (and how many times you've failed to cast them), freed slaves, killed cliff racers, weapon swings and arrows shot, game days passed...
http://www.fliggerty.com/phpBB3/cne/cne_main.php