Google Chromecast can be set up by going to the setup page on a supported device. But in technical terms, what is actually happening on your device that configures the Chromecast dongle? For instance, if I have a WPA secured wireless AP, how does the dongle "listen" for configuration information?
afaik the only automatic way of doing this is Wi-Fi Protected Setup (WPS). However, that wouldn't require an additional device. So it seems like Google is doing something else.