Billboards listen to your car radio, then pitch accordingly:

For example, if the freeway were packed with country music listeners, the billboards might make a pitch for casinos. If National Public Radio were on, the billboards could change to ads for a high-quality car or a gourmet grocery.

The billboards — in Palo Alto, Daly City and Fremont — will pick up which radio stations are being played and then instantly access a vast databank of information about the people who typically listen to those stations. The electronic ads will then change to fit listener profiles.

In the buzzy hum of 21st century commercialism, it's the latest way for businesses to target consumers without wasting money on scattershot appeals. Many auto dealerships already use a similar system to identify the stations people are listening to as they pull into a car lot — and then place ads on those stations.

"You know what this is about? Accountability," said Tom Langeland, president of the Sacramento firm Alaris Media Network, which owns the 10 video screen billboards in California. "People are struggling, the world is becoming a more competitive place, and advertising dollars have been a huge, misplaced factor. Advertisers don't know where their money is going."

Langeland said the technology should be in place within a few weeks on electronic billboards off Interstate 280 at Serramonte Shopping Center and off Interstate 880 at Southland Mall near Fremont. Another sign on Highway 101 in Palo Alto also is being outfitted. Billboards in Sacramento, nearby Roseville (Placer County) and Los Angeles also will use the technology.

In Spielberg's "Minority Report," Tom Cruise's character makes his way through city streets as billboard advertisements scan his retina and then personalize ads for products. [SF Chronicle]