iOS: F.lux, the app that changes your screen temperature based on the time of day, is one of our favourites because it makes your screen a lot more readable at night. Now, it's available on iOS, provided you're willing to jump through a couple hoops.
To install f.lux, you'll need to sideload it on iOS. While this sounds scary, all you'll need is a free copy of Xcode 7, a free Apple developer account, and a Mac (at least temporarily, the app will automatically update on its own once it's installed). Essentially, f.lux gives you the source code for the app, then you build it and load it onto your iOS device yourself. This is how developers create their own apps to test on iOS, but the process requires no knowledge of coding at all. The process is the exact same as the f.lux knock-off, Gamma Thingy, we talked about a little while ago. F.lux has an official guide to walk you through the process below. When you're done with the installation, f.lux will work across iOS, changing your screen temperature based on the time of day.