I am sorry for not being able to come up with a more descriptive question title.
For getting remote metrics I use nrpe on linux-based machines and nsclient++ on windows-based machines.
If I need to check, for example, if a certain server is reachable from another server, I'd just run an appropriate plugin (like check_http) using nrpe. I've recently faced the need to do the same thing, but the remote server is running windows so I am stuck with nsclient++.
Now, you can run scripts from nsclient++, so you can write a vb/powershell script, that will do that. Before I do that, however, I'd like to know if there are any existing solutions (surely, I am not the only person on Earth who had to deal with this).
At the very least I'd like to have something, like check_http, that I will able to run using nsclient++.
this should be, what you are looking for: http://www.nagioswiki.com/wiki/index.php/Using_NSclient_and_NagiosPluginsNT_for_Service_Delivery
It is a combination of nagios plugins for windows and nsclient++.
You could try to turn the Windows server into *nix with cygwin, run an ssh server on the Windows machine, and then use check_by_ssh :-)
Just as you can run the NRPE/NSclient checks locally, you can use psexec to run them from a remote machine.