One of the things the mobile industry has been working on for ages has been the use of a mobile phone as a security token or trusted device. Replacing things like the RSA keys, and physical paper documents we use to do things like get on an aeroplane. I was impressed recently on coming back from Düsseldorf that I could get a boarding card on my mobile for my flight.
This was accepted at the security gate along with my physical passport, and at the boarding gate I just put my phone on the scanner to read the barcode and was through onto the plane.
I got the mobile boarding after checking in using the Lufthansa mobile site, which then sent me a text with a link to the boarding card web page.