windows 2008 has it built in so you can trigger a task to run (just like a scheduled task is triggered by a schedule) based on an event id. for example, take the event you see when your task fails, create a task to call a powershell script that sends an email. pretty easy to pull off and you dont need to install anything extra on the box.

what i've also done for customers that addresses what you mention is actually from the other end we look at the journal mailbox(es) in exchange. with powershell you enumerate the item count in the mailbox and if it's over a certain threshold, you call the rest of the script that sends the email alert.