<i>Not the parent poster, but I also worked in the tech space of outdoor advertising.</i><p>The camera based systems I saw used facial detection. The vendors were very keen to refer to &quot;detection&quot; not &quot;recognition&quot; since they (supposedly) only looked at faces and analysed them for demographic information, they didn&#x27;t track you as an individual. (I&#x27;m sure they would have eventually - there&#x27;s too much money at stake to <i>not</i> track someone&#x27;s movements and show them relevant ads)<p>There&#x27;s lots of vendors of facial detection software than claim to be able to detect:<p>- age<p>- gender<p>- ethnicity<p>- mood (though that one&#x27;s a bit suspect)<p>- where your attention is focused<p>Most of the software does a decent enough job of most of those.<p>Some vendors would use the camera to track how many people watched the ad, their age&#x2F;gender breakdown, how long it held their attention, etc. In those cases it was just about providing &quot;performance&quot; reporting to the advertiser. Often they would have minimum audience guarantees, and would keep running the ad until it hit its levels.<p>Others tried to target specific ads to specific demographics. They&#x27;d have a bunch of ads loaded, and would pick which one to show based on the demographics of current audience.