While there have been non-practical propositions on how to do just that in the past (most depending on a backend or on online transactions – you can imagine the queues when there’s network lag, or if the network is down), there are already viable technologies that exist now that can be competing or complimentary.
As the article suggests, one option is to use a dual-interface USIM, to be used as your usual GSM SIM, and as a contactless payment and/or physical and logical security access device. The other is to use NFC (near-field communication), an upcoming contactless technology that’s been getting a lot of hype for its promise to deliver true contactless integration to the masses (another article altogether).
In short, NFC is the type of technology that allows bi-directional communication – your token is also a reader. Contactless payment is only one application, but with its bi-directional capabilities, you can imagine tapping your phone (or whatever NFC-enabled token you have) on a poster for a concert and you have the option to immediately buy a ticket, putting it on top of a print ad and getting more detailed information, flashing it over a grocery item and getting possible recipes – i’m sure the list goes on…
Pretty exciting stuff.