I have a Galaxy Nexus running Android 4.4.4. Under Settings->Display & lights, there is an option called "Cast screen", which can be toggled on and off. What devices and/or software are compatible with this feature? Is this for Chromecast, or something else? Is the screen picture/video sent via WiFi, Bluetooth, or USB?
It is meant to work with Chromecast, but there are other desktop applications like Reflector 2 that will work with the cast screen setting. You can use the Chromecast app from the Google play store to do the same thing.