There are more great ideas for instant marketing every day and this Pepsi initiative is a first - but however clever the clever the idea, you have to follow it through ALL the way

Technology called audio-fingerprinting recognises the ad - and a coupon for a free 20-ounce bottle of Pepsi Max is downloaded to your phone instantly.

Pepsi is to honour as many as 50,000 such coupons as a way of getting people to try Pepsi Max - as well as trying out (much more significant) the potential for interactive TV ads.

IntoNow's "fingerprinting" knows not only what consumers are watching, but also if they're watching it live or delayed on a DVR or other recording device. I pointed my phone at the YouTube clip of the baseball "Field of Dreams" ad and it worked.

The coupon with barcode was downloaded - I was customer no 502 - and I was asked whether I wanted to use it at the pharmacy chain CVS or the chain store Target.

I chose CVS. there was a little  difficulty with the store when tried to collect my free Pepsi. The manager told me they had a written instruction not to accept smart-phone coupons . "Could you print it off, " the manager asked. After negotiation, the coupon was accepted as a "gift card" and I walked out with my free $1.80 bottle of Pepsi Max.

The deal is the first major brand tryout for IntoNow based on the audio fingerprinting technology developed by Auditude earlier this year. They spent years recording and fingerprinting TV programming from 130 major US networks. Initially the idea was to recognise shows and insert ads online; now it is being used to allow consumers to "check-in" to shows to let their friends know what they're watching.

CEO Adam Cahan told AdAge it took the technology only four to 12 seconds to recognise a given clip. "If it has aired on TV in the last five years, its in our catalogue," he said. "Our coverage is pretty big. There are a few things that are missing. We don't have movies until they hit the premium channels, and we don't have truly local content."

But a big audience is already tagging TV shows -- there have been 3million tags and 600,000 downloads since the app was launched in January.

I asked Pepsi in the UK if they planned to try it out in the UK (obviously not with a baseball ad). They're getting back to me.