Caught a report on the news last night about using your mobile phone to check-in at the airport. Vague, missed half the item. New service at Narita, part of what seems to be called "e-Aiport". Follows that the service will be "e-Checkin".
Present a barcode capable mobile to an ATM-like machine. The barcode generated by the phone is read by the machine which retrieves a previously made reservation. Passport is inserted (same way as a bankbook is read in an typical bank ATM, in Japan at least) and once the passport and reservation are matched a boarding pass is issued. At the gate, the boarding pass is read and pulls up a picture of the traveller for the staff at the gate to match with the person in front of them.
Will check the facts on this and update.
Horrible privacy and surveillance/tracking potential. Secure and simple. Mobiles for identity, purchase. etc. No end to what they'll do (might use them for telephone calls, occasionally, too.)