I wish there were some way for it to detect the ambient light of the room I'm in. Late at night I prefer the warmest setting. But I feel like I'm constantly adjusting f.lux based on where I am. If I'm out, I can't control the lighting of the room. At home in the winter when it gets dark early, I don't want to turn the lights off at 5pm. But if I don't adjust f.lux, it hurts my eyes.
My grandfather had an ancient color TV with this feature. You could press a toggle button on the front that would open or close an iris over a sensor, and the TV would adjust the on-screen color to match the room lighting.
As long as it can be set by command line or has a simple config file it shouldn't be that hard to set up a daemon to take a picture with a webcam then munge the color temp and brightness and adjust f.lux accordingly.