Disney Research has worked out a way to use the microphone and the huge processing power of todays' smartphones to embed in the audio channel of a movie (but it can be a music through a radio broadcast and any other digitally produced sound) data streams.
Their idea for application is to have packed in a movie audio channel additional information that are transmitted via the audio signal but on frequencies that are not intercepted by our ears. These frequencies are captured by the microphones of smartphones in the audience that can sort out the embedded information communicating one another.
You can download the full paper here (interestingly it is made available through Amazon AWS). The difficulty is to be able to hide in the audio channel an information stream of worthy dimension since the point is not to send SMS like packets but real information flows. To do that one microphone would not be sufficient and Disney researchers have though about using an array of receiving microphones like the ones that populate a cinema hall.
They notice that in most cinema the radio signal is blocked so they wanted to create an alternative way of funnel information to the audience, still making it visible on their smart phones screens.
What I find interesting is that this "IS" a 5G application. We are harvesting the collective power of smartphones (at the edges) and create a local network that can process and exchange signals.
The other things that attracted my attention is that in this solution smartphones microphones are used as "sensors", like I claimed it was a possibility in a post some time ago talking about sensors for smarter cities.