QR codes could make entering secure keys in to mobile devices easier. Variations of Wi-Fi quick set-up can also be made reasonably secure, implementations just suck.
In a world of unlimited bandwidth, I'd prefer to leave my wi-fi open (I won't live in fear of terrorists war-driving on my specific block), but I saw this framed QR code for wi-fi password idea on Pinterest: http://www.apartmenttherapy.com/share-your-wifi-password-wit...
