Just an idea - what about to test VMAN itself?
Create a new Alert:
1) Severity: Informational
2) Item Type: VM
3) Search Query: vm.name:"VMAN" (replace VMAN name)
4) Evaluation: Performance data collection
5) setup either e-mail notification or SNMP Trap
If you get Email / Trap then all services work as expected. If not, something is wrong.
I sent this very question to tech support and they got back with monitoring the tomcat6 service, using net-snmp, and monitor the postgres process. Your idea is interesting though.