Ugh. Apple can go to hell. I use F.lux as my main point about the problems with Apple's walled garden. It's available GRATIS for iOS but Apple censors it so you have to jailbreak. The idea that Apple works to thwart this means they are actively hurting people. This specific issue was step one on my long journey to GNU/Linux and leaving Apple and proprietary software behind. Yes, F.lux (Redshift for me now on Linux) is that valuable in my opinion.