Sunset Lets You Use Your Phone Without Losing Your Night Vision
Android: If you're stargazing at night, or just somewhere dark and you don't want to be blinded by using your phone, Sunset for Android is a simple screen filter that applies a reddish overtone to your display so you won't lose your night vision.
The app was built by and for amateur astronomers who wanted to use their phone without losing their ability to see while using telescopes or binoculars. It's just as useful for people who need to use their phone in a dark restaurant or movie theater without annoying anyone or signaling to everyone around that they've turned their screen on. The app has four different screen filters: "dark," a standard grey filter; "midnight," a dark filter that's slightly blue; "sunset," a filter designed to limit the amount of blue light you see before bed (blue light makes it harder to fall and stay asleep, if you don't remember); and "red," the filter originally designed for amateur astronomers and stargazers, which lets you see detail without being bright or distracting.
Sunset isn't the only app like this. Previously mentionedTwilight is more like F.lux for Android, and offers a similar red tint, only it's applied as the day progresses. If you want to try Sunset, you can grab it from Google Play for $1.