SIM does not monitor the general health of the agents/services directly. There is also no event generated (that I am aware of) that goes to SIM if they are down. That is not to say you could not script something (maybe using a scheduled task that will send an SNMP trap if the services are down).
What you may want to do is 1) monitor the agents with another tool (SiteScope, for example), or 2) Check the daily identification task to see if there were failures - if so, you can be somewhat sure there are failed agents or communication problems. This is a good idea to do at least weekly so you can ensure servers are communicating properly with the CMS.
You could also create an event handler that will email you if you see a specific message - i believe it is "data collection timeout" where SIM tried to connect to a machine for the identify task, but could not. The downside is, if a server was down, you would get a "false positive" - same for the identify task method i mentioned above.
I have asked this specific question to our HP guy helping us with SIM and that's what we came up with.
