A rudimentary script that stores the Woot Private Message count (default of 0) and sees if it changed since the last time. If it does, alert() the user to the difference.
This only works on a forum page and the private message thread page. If the private message area (not an individual thread) is the loaded page, there will be no alert.
You will be alerted when you send a private message. So, if the difference is 1, just ignore it.
The alert is one time (per number change) only.
This does not take into account what the messages are. So, if a message was deleted and a new one comes in (at the same time) there will be no alert. This seems like a rather unlikely case.
After a deletion, the new number is stored. So, further messages should be noted.