The developers over at F.lux Software LLC have created something for the Cydia store that steps away from the standard tweaks that we have come to expect. Their f.lux package is a tweak that is designed with user visual comfort in mind and warms up the iOS device screen in an attempt to match the lighting during the evening.
The theory of the software provided by F.lux is that it isn’t visually comfortable to use a mobile device or computer under the same lighting conditions twenty four hours a day. They believe that as the external lighting conditions change, the lighting on the mobile device should also change to reflect this, which is exactly what the f.lux Cydia tweak does.
When installed, f.lux warms up the colors of the iPhone display when the sun is setting and does the reverse in the morning by returning the device to its native daylight colors. There is actually a great deal of science and research applied to this topic, with a large percentage of technology users believing the display should be about brightness rather than actual color. It has been proven that blue light is great for the bodies circadian rhythm, however in the evening it detracts the body from sleep and becomes extremely detrimental to health in the long-term.
When installed, f.lux has a few configurable preferences in Settings.app which includes being able to choose the lighting system for the evening and day time, as well being able to toggle the tweak on or off. There is also a OS X version of the f.lux software over at the official site.
F.lux is available as a free of charge download from the Cydia/Telesphoreo repository and is compatible with iOS 4.0 and above.
Of course, you will need to jailbreak your device to install this tweak. For jailbreaking the latest iOS 5.1 (tethered), follow the instructions posted here to jailbreak using Redsn0w, or here for Sn0wbreeze. For jailbreaking iPhone 4S and iPad 2, you can simply follow our step by step tutorial posted here to jailbreak iOS 5.0.1 using Absinthe on Windows or Mac. Those of you with an iPhone 4, 3GS, iPad 1, and iPod touches can use Redsn0w or Sn0wbreeze to untether jailbreak on iOS 5.0.1.