In December 2015, a Salesteam from Shazam music recognition app came by our office in Amsterdam to sell ads targeted and synchronized with TV commercials. Earlier that year they had done this with several big US advertisers: iPhones (and/or Android devices, I don't remember but their pitch was specific about the supported platform) with the Shazam app were constantly listening via the phone mic, when they recognised a Pepsi commercial, the app would register this and next time you open Shazam you would see a targeted ad. You had the ability to then target users even in other ad-supported apps and follow them via the Apple Advertising ID.