I use a b&B backlight controll widget, it doesn't function 100% (ie won't turn backlight below 9% and the dimmest setting is somehow 22% O.o). But this is because of android on our devices not the app. Its still allows for the backlight to be lowered further than android would normally allow to save battery.
I had the complete backlight turnoff incident once, but I knew my android somescreens well and was aple to find the app, click on it and increase the backlight again
