Hi,
I've tried to use xscreensaver locking my Z automatically as I switch it to stand by. I couldn't managed it.
But you can start it with $HOME/.profile as follows. (It starts X11 at login and xscreensaver will be started with.)
# here you can do some settings...
if [ $TERM = "linux" ]; then
(sleep 3; xscreensaver )&
startx
exit
fi
I have to say that I don't use it anymore, and this is only as I remember on it. (I didn't find any saving about my tests.)
I hope it helps you. Anyway I would use some minimal protection, too.
Best wishes,
Tamás