While evaluating your service, I noticed that if you pause a monitored windows service, no alert is triggered.  If a service is in any state other than "Running", it is not up and should trigger an alert.  

This suggests to me that you are saying you are monitoring the service in the UI but you are actually monitoring the process under the covers.  What if a service hangs at starting or stopping?  The exe would technically be running but not functional thus in an error state that you would likely miss.  Services are not processes, they are up when windows says they are up, you have the query the operating system for it's status, not simply looking for the underlying executable.