Are there any known issues with starting rwhod on multiple UNIX systems on a network...? I.e. if I get hacked on one system does the hacker own me and my systems/network?
-KJ

cve.mitre.org lists a few historical vulnerabilities for rwhod, but nothing recent. In general it's never a good idea to run any network service unless you absolutely need it. The more services you run, the higher the possibility is that one will have a vulnerability and the more things you have to worry about patching right away.

If you did run rwhod on all your machines and an attacker was able to compromise one of them through an exploit of rwhod, it is extremely likely that they would systemically take over every other machine on your network that was running the service.

Very logical...

In my case I am looking for a way to monitor (some) real systems that are split up into (numerous) virtual systems.

any-who I am trying to have each system watch the other(s) with the least downside and no extra costs (real dollar, and risk)

I currently use a simple ping script that I wrote but it is not as good as I would like and it is not giving the data that ruptime returns that would be very helpful
For example is my app working when I think it should at any given time of the day

I tested rwho between my dev and another system temporally before posting my first post. And it returned all my active cron jobs with owner and job name a crossed the two systems. Thus with some parsing I can make a simple tool to monitor if the system peers are working as they should.

any ideas on what else to look at?

... i.e. in the UNIX tool box...?

Use ssh in with private keys that do not have passphrases. Of course, you'll want those accounts to not have privileges to modify anything on the system, but they could get uptime, load, running processes, etc.