The movie "Minority Report" is coming to pass. Okay, probably not the part with the slime-covered "pre-cogs" who can see into the future. But digital out-of-home technology is making possible a revolution in addressable, interactive advertising in public places, well before the movie's setting in 2054. In fact, the question is no longer one of technical limitations, but which limits advertisers choose to observe voluntarily, and which are imposed by consumers through regulation.

The interactive element is already there, and because it is a public medium, it promises to engage large numbers of people at once. According to Dale Herigstad, who developed the design concept for Minority Report (and who said earlier this year the futuristic interface "doesn't seem that far away now"), interaction serves to "activate" place-based digital media, with a few early adopters drawing an audience into active participation. That's the principle behind the interactive touch-screens Herigstad helped design to promote Accenture in Chicago's O'Hare airport, which allow travelers to browse and arrange text and video content on highly visible digital displays. In this scenario, the individual's browsing becomes a public event that can engage other passers-by.

Soon, you'll be able to interact without having to touch anything.  By tracking their actions with motion sensors, gesture-based interfaces allow users to control digital displays with roughly the same precision as a laptop track-pad. Currently this technology is being used by one company, Reactrix, to deliver advertising alongside interactive social entertainment, like games and art programs projected in public places. But Reactrix CEO Mike Ribero said in a recent interview that he envisions the displays becoming points of sale, using credit cards with embedded radio frequency identification (RFID) chips, or cell phones that double as credit cards. Digital out-of-home could become a hybrid sales platform, combining e-commerce and in-store retail transactions.

That takes care of the interactivity. But what about addressability? To be acceptable to the American public, of course, any system delivering personally addressable advertising in public places must have a clear opt-in. This will likely present at least as many difficulties as opt-ins for email marketing or behavioral targeting online (with serious ramifications if consumers feel deceived about the terms of the opt-in, or simply fail to acquaint themselves with them). But once these obstacles are overcome, advertisers can deliver messages, coupons, and promotions with much greater efficiency in terms of both timing and location, taking advantage of proximity to the point of sale. Again, it's already here: ShopRite is delivering e-coupons to shoppers based on their physical location within the store itself. In partnership with MediaCart Holdings and Microsoft, ShopRite tracks individual purchases and delivers discounts via digital displays on shopping carts; the displays also allow brand advertisers to reach the shopper during the supermarket visit.

The SmartCart system relies on shoppers opting into a supermarket customer loyalty program. But consumers could also choose to be identified in other ways, including via their cell phones, or credit cards with embedded RFID chips. Driver's licenses may soon carry RFID chips as well. Last year, Cooper Mini staged an addressable public advertising campaign in San Francisco, with digital billboards displaying customized messages to Cooper Mini drivers who elected to participate, by reading RFID chips embedded in their key fobs. RFID chips can also be incorporated into clothing, and can even be inserted into the human body without ill effect; RFID tags have already been inserted in over a million pet cats and dogs in the United States, and a small but growing number of Americans have linked their online medical records to RFID chips embedded just beneath the skin, so doctors can call up the records with a scan. The chips are also being used by a private resort chain in Europe for "VIPs" who want to avoid the hassle of identity tags and credit cards.

But RFID chips may be unnecessary given the emergence of technology that can scan the faces of passers-by to determine their age, gender, and ethnicity. This facial-recognition technology has been incorporated into "billboards that look back" by a company called TruMedia, the New York Times reported in May, and allows out-of-home advertisers to serve up advertising that targets viewers by their demographic characteristics. The news caused a small controversy, with predictable objections on the grounds of privacy and counter-claims from TruMedia, which vows it doesn't record any of the data and would never share it with other companies.  

But the technology's actual capabilities go far beyond anything touched on in the Times article. The facial recognition software was developed by the Israeli military for active surveillance, and can not only scan and record facial features, but match them up against a database of known individuals at the rate of about 100,000 faces a second.  

If consumers gave their consent, cell phone IDs, RFID chips, or facial recognition technology could identify them wherever they go, allowing advertisers to deliver targeted advertising that "follows" them from one place to another. At this stage, digital out-of-home advertising begins to merge with behavioral targeting of the sort already in use on the Internet, according to Dave Martin, director of interactive media for Ignited. Agreeing with Herigstad that "'Minority Report' isn't so far away," Martin predicted that "digital, addressable media will go from just your PC to your living room, your kids at school, in your car, at work."

Ultimately, advertisers should be able to combine demographic data, Internet usage, physical location, and purchases with credit cards and cash (including plane tickets, car rentals and hotel reservations) to invent the next generation of roaming, behavioral, out-of-home targeting (ROBOT?). For example, as you walk down the street, you might see a series of video ads telling a multi-part story, delivered by screens in different venues. To do this, advertisers would simply have to aggregate different place-based networks, a service already provided by companies like SeeSaw and AdCentricity. This is already possible online; if consumers opt in, it would simply enable the "real world" version.

Of course, that's a big "if." Clearly advertisers will have to offer sufficient incentives to overcome the "creepy" factor. But the new technology offers tons of possibilities. What if you received a 5% discount on everything you bought, everywhere? What if you didn't have to wait in line to check in at the airport? Or show ID when buying alcohol? Didn't, in fact, have to carry a wallet or pocketbook at all?

And it gets even weirder. For people still leery about interacting with digital displays in public, a new technology from Ambient Corporation allows "voiceless communication" via cell phones. The Ambient system uses an unobtrusive neckband to sense the nerve signals from your brain to your vocal chords, determining what you're going to say, then "saying" it with an electronic voice that your interlocutor can hear -- while you remain totally silent. The system, demonstrated by Michael Callahan of Ambient Corporation in March, currently only recognizes about 150 words. But once the vocabulary grows, it would enable a variety of interactions with the Internet and, one imagines, digital out-of-home displays. Callahan said it would allow the user to send voiceless queries to Google, for example, which implies that you could also use it to complete a commercial transaction in a public place without moving or speaking out loud.