Biztalk fires WMI events when it suspends a message. There are a number of tools that can monitor these events Microsoft MOM being one, but also CA-Unicenter, Tivoli, NetIQ, etc.
These management tools allow you to specify the action to take on any event, they will aggregate events (if you get 10,000 errors you will not send 10,000 emails).
There is even a MOM Management Pack for Biztalk.
http://www.microsoft.com/downloads/details.aspx?familyid=9E07C538-9ED4-41EA-9914-35DF6EFFB078&displaylang=en
If you wish to write your own here is a starter from Martijn Hoogendoorn
http://martijnh.blogspot.com/2004/07/biztalk-2004-suspended-queue-listener.html