Not ultra-sonic but this app sends photos from iPhone to iPhone using the speaker and microphone. https://itunes.apple.com/us/app/acoustic-picture-transmitter/

Not ultra-sonic but this app sends photos from iPhone to iPhone using the speaker and microphone. https://itunes.apple.com/us/app/acoustic-picture-transmitter/id415136803?mt=8 https://itunes.apple.com/us/app/acoustic-picture-transmitter... Fun to play around with and think of the possibilities of using sensors in unintended ways.