If you're reading this on Tuesday morning, the only pint on your mind probably involves caffeine. But trust me, lager is much more interesting this morning, because Carling has launched a new ad campaign and it just might point to the future of advertising.

Don't expect to see this ad in the usual places. You won't find it in newspapers or on telly. And even the web isn't the place to fully appreciate how clever it is.

No, to see the new Carling ad in all its glory, you'll need a mobile phone. And not just any mobile phone; you'll need an iPhone. Mind you, you'll also have to redraw what you think of when you think of an ad campaign, too. Because the new Carling campaign is not only the best example to date of mobile advertising, but it also stretches the definition of what advertising is.

The new campaign is called the iPint and it blurs the lines between advertising and mobile applications. It works like this: you take your iPhone (or you would if you had one, which you probably don't and neither, regrettably, do I) and you go to iTunes and download the iPint application on to your phone.

The iPint is basically a game that makes superb use of the iPhone's wonderful accelerometer. Jargon translation: the accelerometer is the thing that makes the iPhone's display tilt from landscape to portrait and back again as you rotate it.

To play iPint you have to swivel the phone around to move a pint along the counter of a bar, around various obstacles and into the waiting hands of a thirsty drinker. There are various levels of play and it's not as easy as it sounds. Anyway, once you've completed your mission successfully, you are rewarded with an empty glass that fills with Carling before your eyes. You can swill the beer round the glass and "drink" it up by tipping the phone. Go to carling.com/ipint and you'll find a little demo.

Beattie McGuinness Bungay

The application was created by Beattie McGuinness Bungay, who worked with the Swedish developers Illusion Labs. I'm not going to pretend that this is really, at this stage, much more than a clever stunt. After all, BMB also does some rather splendid TV and print advertising for Carling that no doubt sells many more pints. And although the iPint is top of the free applications chart on the games section of the new App store and at number two in the iTunes general applications chart, that still doesn't mean you're likely to meet many real people who've actually seen it yet. Which is a shame, because it's stunning.

The iPint is far more engaging and viral than almost any of the advertising you're likely to see this week. And while it's been created by an advertising agency, it encapsulates one of the real challenges facing the traditional ad industry.

Mobile phones are the medium of the future. If you don't believe me, take a look at the article in the current issue of Wired magazine that illustrates Google's determination to be part of the mobile future. The Android open source wireless interface that Google is developing will help turn mobile phones into multi-devices offering the sort of web access and computing applications we're used to on our desktops, with telecoms thrown in.

And to encourage mobile handset manufacturers to embrace Android, Google is offering the chance of advertising partnerships that could help grow the mobile advertising pie from $1.7bn (£860m)in 2007 to a forecasted $12.8bn by 2011. Our mobile phones will become the gateway through which we communicate with the rest of the world, and through which the rest of the world communicates with us.

But while technology is moving quickly to chase the opportunity, there are an awful lot of ad agencies that seem to be looking the other way. Fair enough, to a point. Up until now mobile advertising has been niche, promotional rather than brand-building, and creatively impoverished. You can see why it's not been high on the ad agency agenda. But Carling's iPint throws the game wide open. It will be interesting to see who's fit to play.