So here goes...
I'm running MS-IIS on the same server as RadiusNT.  So I created a /RAD
directory under /WWWROOT/SCRIPTS and setup an execute-only alias called
/RAD pointing to the /SCRIPTS/RAD directory.  In this directory I put the
following batch file called R.BAT :
	@echo off
	c:
	cd \radius
	radlogin.exe mphillips blah
	if errorlevel 0 goto result0
	if errorlevel 1 goto result1
	goto end
	:result0
	type c:\radius\radcheckgood.txt
	goto end
	:result1
	type c:\radius\radcheckbad.txt
	goto end
	:end
In the C:\RADIUS directory I put 2 text files.  RADCHECKGOOD.TXT contains:
	Content-type: text/plain
	.
	
	<html>radius running</html>
and RADCHECKBAD.TXT is an empty file.
Now setup a new host in WhatsUp with the IP address of your RadiusNT
server.  On the 'Services' tab create a 'Specific Service'.  Filling in the
following fields:
	Enabled: checked
	Port: 80
	Send command on connect: GET rad/r.bat\r\n
	Expect after connect: HTTP/1.0 200 OK
	Timeout: 10
Now, if all goes well, every X number of seconds WhatsUp will remotely run
the RADLOGIN procedure and, if it's successful, will send back a valid http
response, otherwise it will send an empty (invalid) http response.  You can
also test your server with a web browser by going to
http://www.yourserver.name/rad/r.bat.  If you get a 'radius running' back
then you know it's working.
Mike