Check out the video below, so that you can see how it works.
After installing SleekSleep, you can go to the Settings to perform further configuration. In the Settings, you have the option to enable it only in Portrait mode or disable it while calling. You can also add a Settings toggle in Control Center so you can enable and disable the functionality from anywhere in iOS.
Battery LifeBut, since this tweak is requiring that the proximity sensor stay active, this will ensure than your battery will drain faster.
Keep in mind that this tweak only works with iPhones due to the proximity sensor requirement. SleekSleep works fine with iOS 7.