Yahoo has filed patents for a smart billboard that uses cameras, microphones and other sensors to collect data on passers-by for ad targeting purposes.

“In the past few years, online advertising has quickly become the primary channel by which advertisers reach out to consumers,” reads the patent application. “The ubiquity of mobile devices and the ability to craft individualised marketing strategies to meet the needs and interests of specific consumers have made a compelling case for such techniques as the most efficient use of marketing budgets. Nevertheless, a significant portion of such budgets is still devoted to more traditional channels.”

The idea is to bring the targeting and tracking capabilities of online advertising to OOH. One example given in the application is sensing the make and model of vehicles driving past a billboard to put together a demographic model that can be used “in conjunction with information about the time of day and/or the day of the week (e.g., Monday morning rush hour) to select advertisements for display”.

The sensors would also be used to detect whether people are paying attention. The patent mentions eye tracking, to detect anyone looking directly at the ad; proximity and image recognition, to determine if they slow down as they pass the ad; and even using microphones to check for ad-related keywords being spoken in nearby conversation.

The patent applications were submitted in March last year, but have just been made public by the US Patent and Trademark Office – a bad bit of timing for Yahoo, given last weeks revelation that the company had helped the US government scan the email accounts of Yahoo Mail users.