You can use montoring tool for this then.
configure RSCD service in such monitoring tool, so whenever the service goes down it will notfy you.
A nagios (or other) check that runs agent info I think would be ideal.
It's not real time, but it's common practice to run an Update Server Properties job against all your servers at least once daily. This will ping all the agents and prompt them to report back. If the RSCD service is not running the Server property called AGENT_STATUS will return an "agent is not responding" message.
Is BSA you can create a Server Smart Group with the logic:
Any Server where AGENT_STATUS equals "agent is not responding"
At any time you can expand that Server Smart Group to see if any agents aren't reporting back properly. Whether because the RSCD service isn't running or any other reason the application server cannot contact the target agent. Not exactly what you were asking for, but it's a recommended admin task in BSA.
Daily, or however often you're deploying: which may be as rarely as weekly.
Then I use a smart group to identify known-down servers, and check back in on those servers more often.
You can use BMC's own monitoring tool:
There is a parameter: Managed Host/State that (by default) is updated every 5 minutes to indicate the status of the RSCD Agent on that Managed Server:
Available, Unavailable, Not Licensed, Not Installed