OP, you may be interested in the following:
TV detector van - Wikipedia
Also, listening to the IF of car stereos was something conjured up for advertising back in the '90s if I'm not mistaken. How it worked was say you drive at a mall and the mall had the equipment to know what station you were listing to. Now they have data for marketing... Today, marketing data is absolutely EVERYWHERE in ways you can't even fathom. In India for example there is a sub audio sound transmitted from certain TV channels or whatever and your phone would hear this and report back to data broker central to know what channel you were watching, the time, device ID, etc. In the U.S I don't think they do this, but could be wrong. The technology could be used in different ways as well.
God help you if you have an Amazon smart speaker... There was an open source alternative called Mycroft (not related to Sherlock Holmes lore) but it's been replaced by something else and I haven't kept up with the project.