I'd like to see this also... I don't believe there is currently a built in feature when using monitored process.
Closest you could get with built in would be to change process to run at a scheduled time... then if there is a problem when it runs (e.g. file not present) you could easily get an alert.
I prefer the monitored process myself also because I am working with vendors that don't always deliver the input files on time, I want the process to go ahead and kick in whenever the file does arrive instead of making me have to manually kick it off, but I have the same issue with monitoring to alert when processing doesn't occur.
My current thinking is to write a service to do this using the Automator API.
If anyone else has a better idea please share!