I wrote a very similar web implementation 12 years ago as a proof of concept - if it got the go-ahead, the plan was to test it with some commercial TV broadcast

I wrote a very similar web implementation 12 years ago as a proof of concept - if it got the go-ahead, the plan was to test it with some commercial TV broadcasting in the UK where a ultrasonic short code could be sent to phones using an app with a Web view, or possibly native app. Sadly never got picked up, although we proved the concept could work - but it certainly had it's challenges. https://github.com/tanepiper/adOn-soundlib https://github.com/tanepiper/adOn-soundlib https://github.com/tanepiper/adon-ad-platform https://github.com/tanepiper/adon-ad-platform