SuperDim - This requires root privileges on your device and a backlit LCD screen (not OLED).
SuperDim lets you dim the display to very low levels--lower than the OS normally allows (that's why you need root privileges)--to save night vision. This will be particularly useful for serious amateur astronomers.
On some devices you can also turn off LEDs (e.g., power LED)
Pencerahan Brightness is an Android application, which allows you to easily adjust screen brightness. You can increase or decrease the screen brightness without the need of searching into the Settings-Display menus. It is great for saving battery life
Rotation Toggler is essentially an auto-rotate screen toggler application that allows you to enable or disable Android's auto-rotate feature. This is useful especially when you don't want the screen to change its orientation when say..you are reading an ebook or browsing a site and don't want your browser to change its orientation
Multi-Purpose Safety Light - Now for only 99 cents! Turn the Multi-Purpose Safety Light on, and you can be safe when jogging, running, bicycling, or riding at night. This simple tool offers different types of illumination such as LED lights, Radial lights, and Flash lights. Colors and flashing speeds are adjustable
Brightest Flashlight Free - Turns on all available lights. Brightest Flashlight App – Free of Charge * Turns on all available lights on the device * Camera Flash LED at Maximum
LED PartyBoard - LED PartyBoard - Be the center of the party! LED PartyBoard lets you type in a text, choose color and speed, and scroll the text sideways like a LED display on your Android! As seen on billboards, stock tickers, banners and traffic signs everywhere
Flashlight with LED Support - Incredibly simple and yet very useful Flashlight application. Will use your mobile device's LED if it has one. Otherwise will fallback to compatibility mode. LED functionality works on Android 2
