Hours of forum time used?

[memobug]

I was wondering if there exists already a hack for keeping stats on how many hours a member was online. I am thinking of maybe

1. a session variable that shows time logged in for this session
2. a grand total cumulative variable that shows hours logged in since registration
3. a yearly total that shows hours used since the calendar year
4. a total count of threads viewed (not unique threads, maybe just the total times showthread was executed for that member) for the year and forever

The idea being, when I go hitting up members for donations, I can customize the email a bit and say something like,

Dear Bozon, we're happy you're enjoying our forum and have found it of use to you. Unfortunately, these services cost money for server bandwidth and space. Our records show you were logged in for a total of 300 hours this year and read 5000 forum message threads. Donations are completely optional, but at this user level we recommend a donation of $30.

The idea being we demonstrate that there is utility/responsibility.

Regards,

Matt