ah so your talking about sms sus fp, well you would have to actually modify the package to include it....which would make its use kinda impractical. this was more for distribution via sms installer package
Although I'm sure you could tweak the package sus makes to do this.
The code in an installer package is nothing more than this, just before exit:
item: Execute Program
Pathname=%win%\Shutdown.exe
Command Line=/L /R /T:60 "Need to reboot to finalize software installation" /C /Y
end