137914 Scroll tracker & time script

I need a script that can: 1. measure the exact time someone has been on your site in seconds 2. measure how far down your page your site visitor has scrolled, in pixels. That's all I want this to do, nothing else. This has been done before, for example as a feature in [login to view URL] (see the page, they have it as a side thing in the features for their product) I'm assuming you can do this fairly easily in PHP and with the results entered into MySQL database. Let me know how you'll do this when bidding. I want it to be as simple & easy to use as possible (in particular try to make it easy to install) so try not to make this any more complicated than it needs to be. I want the script to also give the average visitor time and average pixels scrolled as well. This project is for certified programmers only and so the winning bidder should get plenty more work from me in future. *I will retain all rights to ownership and distribution of the script.