Author of f.lux here --<p>This build of f.lux prefers to use notifications (you can turn off the Notification Center ones).<p>The screen settings we&#x27;re changing only work when the screen is <i>on</i> but we have to be &quot;ready&quot; when you unlock your phone. We&#x27;re working on a version that does quite a lot fewer wakeups.<p>In our jailbreak version, we just hook the screen unlock and do work then, but we can&#x27;t do this in the jail because we never wake up.<p>In this version the notifications serve as a &quot;wakeup&quot;. If we fail to show a notification, we hit the unlock instead.<p>The battery impact overall is extremely low.