I've an idea here.
create a widget that is similar to Bluezwitch
When you press the button, can lock / off the backlight of the phone,
and when you double tap on the screen it will unlock / switch on the light again.
Is that possible to make such widget?
I always use n900 to text, unlock the phone non stop, times of pressing the power button is uncountable..
I've some knowledge in C++ but I've zero knowledge in developing maemo apps.
guys, any idea?

When I open the keyboard the screen unlocks automaticaly.
Doesn't it work for you?

I think something along these lines is needed for a lockscreen.

The raised portion of the slider switch on my N900 is almost completely worn away, & activating the lockscreen is difficult. Unlocking is not a problem: the top button brings up the slide bar screen when the screen is locked. It would be nice to have a widget to activate the lockscreen, or an item on the top button menu.