Chicago O’Hare airport will join other airports serviced by Delta & Continental in offering the option to use mobile phones as boarding passes. The way it works is a 2d barcode is loaded onto your phone’s screen and the TSA scanners can apparently scan it like a paper barcode.
There are some potential problems though. Sometimes it doesn’t work if the screen is too glossy, on some phones the boarding pass vanishes when a call comes in, its not compatible with all phones etc etc. However its a start and thats a good thing.