During this past year we have done extensive research and development on ultrasonic communication. One of the main outcome is the proposal of a new protocol for communication via sound (and in particular via near-ultrasound) that is simple enough to be implemented on devices with limited computational resources, such as Internet-of-Things (IoT) devices.
We submitted a first version to the IETF that you can see here: https://tools.ietf.org/html/draft-zeppelzauer-data-over-sound-00.
We are now in contact with the IETF editors to get feedback and propose this specification as an Experimental RFC document.
We will keep you posted !