Android: If you use your Android for streaming or video playback over HDMI, you've likely run into the problem of your tablet's screen staying on unnecessarily. This runs down the battery, and there's no need to see the image on both screens. Screen Standby fixes that problem.
Screen Standby simply sets your screens brightness to zero while your streaming/playing video over HDMI. It's a simple trick but solves an annoying problem for those of us who use our Androids as a media center. To use it, just tap the button to turn off your backlight and you're set. You can still see the image you're streaming on your TV (or wherever), but your screen will be off. To get things back to normal, all you have to do is lock and unlock your device.
Screen Standby is free to download, but it does require rooting your device.