Lots of research has shown that computer screens and cell phones reduce the quality of your sleep if you use them at night. I don't think F.lux totally stops this but the software which is free and runs in the background blocks out the blue light at night from computers and cell phones which is meant to be the most damaging to sleep. I was a little suspicious because everything appears to be free (how do they make money?) but there were write ups in a lot of legit places like the Washington Post so I gave it a try. Unfortunately their iPhone version only works with unlocked phones. Otherwise it all seems great.