Not enough information - we can't tell what is required by the backup software that will backup to an IP address... My first suspiscion is that you'd have to install the same backup package on the SME.
You may be able to use the "backuppc" contrib to trigger rsync-over-ssh backups of your OS X servers, but this doesn't use or require any backup software on the remote servers, just ssh and rsync...
You may also be able to setup the SME as an rsyncd server and push backups to it using rsync from the Apples.