f.lux is available for Macs, though it would be nice to have that feature native in OS X. In the meantime:
https://justgetflux.com/
Be sure to uncheck "Automatically Adjust Brightness" in yourControl PanelSystem Preferences otherwise you may see some flickering.
Yeah, this is what I've literally just downloaded. Impressed so far. I also have auto brightness checked, but it seems you have to choose a 'base' level on a Mac and then it just changes it up when the ambient room light gets brighter.