A mounting pile of research suggests that staring at a computer screen for long hours is bad for your health. That should be intuitive, but evidence suggests that blue light in particular can disrupt sleep.
Apps for the PC/Mac and iPhone/iPad (f.lux) and Android devices (twilight) counteract this by filtering out blue light after the sun goes down (or all the time, depending on your preferences). I actually like having it on most of the time except when I’m outside in sunlight because it makes the screen easier on the eyes.
Both of these applications operate in the background and automatically adjust their settings depending on the time of day. That way, they’re as unobtrusive as possible and you won’t be blinded by checking your phone in the middle of the night.
But don’t take my word for it. Let Twilight’s awkward Russian spokesmen tell you all about the benefits of their (free) product: