The FTC alleges that some unnamed app developers are using this tech to monitor the TV shows you're watching. Those warning letters (PDF) mention that the apps "would be capable of producing a detailed log of the television content viewed while a user's mobile device was turned on for the purpose of targeted advertising software and analytics." Told you it got worse.
In case you're unfamiliar (which is totally understandable), Silverpush is a company that uses your device's microphone to listen for ultrasonic sounds to identify when the same person is using multiple devices like a laptop and a smartphone or tablet. This ties the two separate gadgets to the same person and creates a more comprehensive advertising profile based on his or her habits. It's baked into the back-end of messaging app Line and presumably a whole slew of others. Apparently, it can pick up the inaudible audio beacons from TV broadcasts as well.
Silverpush claims it isn't using the tech domestically, but that doesn't make it any less offensive. The FTC has requested that the India-based company alert customers that installed apps could grant third parties rights to keep tabs on their TV viewing habits should said applications make their way stateside. More over, the warning letters request that developers should explicitly ask permission to use your gizmo's mic.
Whether or not this is in use on iOS isn't known, as the dozen notices that were sent only call out apps published on Google Play. We've reached out to Silverpush for more information and will update this post should we hear anything back.