Use an external monitor and perform a
CHECKDATE=`ssh -n @ date`
with a public/private keypair... The -n parameter is in there in case something happens to the public key the server gives back... You need to do this by hand BTW before the automated check will work.
Then just check that the $CHECKDATE environment variable is sane... If it is, then sshd is up & running on the target server...
Changing the command to use NODE_IP and NODE_PORT (And any logging etc you'd like on it) is left as an exercise for the reader. You don't have to do this as a shell script BTW... It could be perl or whatever.
H