On my iPhone 4S (iOS 5), I've set Auto-Brightness to on (in Settings -> Brightness). I haven't, however, seen it do anything. As far as I can tell, my brightness has never changed automatically. The ...
The settings screen Settings ▸ Location Services ▸ System Services in iOS 5.0 contains the following boolean options: Cell Network Search Compass Calibration Diagnostics & Usage Location-Based ...