How to monitor Suspended Queue?

There are a number of options here:

Rather than suspending messages, you can use the a new feature of Biztalk 2006, that allows you to route failed messages. Rather than suspending failed messages, the message context properties are changed and then published to the messagebox. You can have an orchestration or send port subscribe to these messages and take whatever action is required.

Similarly use of scopes and exception handlers in orchestrations allow you to catch errors and take action rather than letting Biztalk suspend the process.

You can also use MOM, to listen for the WMI Events that are fired when Biztalk detects an error. MOM will alow you to send an email in response to an error.