I created a hack for this some while ago. It isn't published yet, but i can give you a brief description how it works:
Mods can set their "unread" posts time to any date they whish. Works for one or all forums. A monitoring system makes it possible that mods can "share" their unread/read messages.
Example:
Mod A browses the subforums 1,2,3 in the morning and makes sure, that no offensive content is posted. He leaves at 10:30 AM and enters that value in the monitoring system. Mod B starts browsing at 1.00 PM, enters the monitoring site and just clicks on the last entry (made by Mod A). His cookie gets set to the correct date and he can start right from the point where Mod A has ended.
