Define the following parameters to the kernel boot options of the clients:
MONITOR_SERVER=IP|HOSTNAME: IP address or hostname of the monitor server
MONITOR_CONSOLE=yes|no: enable or disable full console view, if enabled it's possible to follow all the installation session of the clients (stdout and stderr) in the monitoring interface (default is no)
Usually you need to define the parameters in /etc/systemimager/pxelinux.cfg/syslinux.cfg. This works both if you are installing via network boot or by an autoinstall boot media (CD, USB disk, etc.). For example a monitoring-enabled configuration can be the following:
LABEL systemimager KERNEL kernel APPEND vga=extended initrd=initrd.img root=/dev/ram MONITOR_SERVER=192.168.1.1 MONITOR_CONSOLE=yes
Remember to re-run si_mkclientnetboot (for PXE booting), si_mkautoinstallcd (for autoinstall CD booting) or si_mkautoinstalldisk (for autoinstall USB drive booting) to rebuild the configuration files or boot media to accept the new parameters defined above.