Well, you could always have the servers run the script regularly themselves (as a cronjob)
and then have them email the results, or even telnet back. You could also have the main
server email the remote servers to a specific account, and have the remote servers (assuming
they can accept mail) run the backup program when mail from a certain name and IP
arrives.
P.S. Make a left bracket by typing
[ and a right one by typing ]