I wrote this script to inspire me to stop spending so much time on the internet. This shows a little green clock with the days:hours:minutes:seconds that you’ve spent on any particular website when you role the mouse to the bottom right hand corner of the screen. Move the mouse away to hide it, or click it to remove it if it’s covering something you need to click on.
Greasemonkey and Tampermoneky have no internal memory like databases, so the time is stored in a cookie, which has the downside of being reset when you clear cookies. I’ve read about Recall Monkey, and I've also considered writing a JSON interacting database on my shared host server, but I don't think people would like their every visited website to be stored on my server, for duh privacy reasons.