Full disclosure: I work for an audio beacon startup (in bio).

You're correct about microphone permissions related to the SDK. On iOS, this means displaying the top colored bar when you're using the microphone too... IMHO it's not something you can just turn on and not realize it's being used.

We use our listening tech at concerts and event to distribute triggered content and messages from the speaker infrastructure to attendees' phones (ex. "this drink line is long, go to the other one", "here's a free song from the artist on stage right now", "<sponsor> is giving away a free thing", etc.)