This I would love to see! As it stands, I can quite happily use my Surface until late without feeling any strain on my eyes, but can't do so with my Windows Phone - which I'm much more likely to be required to use later in the night. It's questionable whether or not f.lux could be made compatible with Windows Phones, though, as I'm not sure how much privilege Microsoft allow for their developers. An app which runs all the time isn't exactly something that fits in with Windows Phone.