There is technology such as AOSS around which allows a device to authenticate with a secure WiFi router when a button is pressed on the router, but I don't know if this technology can work continuously (ie. without intervention at the router). Even if it could be made to work continuously, would that be a good thing? I can imagine many man-in-the-middle attacks would use this technology in order to steal information from devices which auto-authenticate without the owner being aware of what is happening.