Hi Rahul,
The alert monitoring is only for failed messages. AFAIK, You can raise an alert an alert when a message coming but you can't do it if it is not arrived in an interval of time.
I think you would need to do an ABAP/JAVA program to control this. You can access to PI ABAP/Java tables to check if any message arrives. Check this threads/blogs:
Monitoring Database Tables in PI for Performance
Hope this helps.
Regards.