iDimLight will not dim your SpringBoard if you have a vWallpaper as your background. It also doesn’t work in a few of the stock applications like SMS, Camera or if you are watching a video in YouTube.
When you start the application, a popup opens and asks you to enter the number of seconds before you like the back light to be dimmed. You can enter any number of seconds you like. If you’d like to disable the app again, just start the app and enter -1. After you have entered the seconds, the app will ask you to restart SB.
If you want this new app you will need to have Ericas Utilities (in Utilities category) installed.
iDimLight is available in the Installer.app through the Bigboss packaging source.