Must be just like owning a PW....
Bind the power button tap to a home button press perhaps.
So use the
err... Thingy that dos1 made... and attach a home button press to the goingToScreenSaver event.
I cant remember which keycode HOME is, or the best way to inject it. (Xdotool?, Or echo a value to somewhere in SYS? maybe something else?)
Bit of homework for you to do there I suppose.
That would work though.
(OR do what the incendiary penguin says)