Android app to send and receive data via ultrasonic stream

I need an app that can send data (ex. a GUID or string) from one Android phone to another using an inaudible ultrasonic transmission (about 20-22 KHz). The sender app should have a text field with the data I need to send and the receiver app should be able to pick up the data and display it (toast or alert). This should NOT use WiFi, only through the Android phone's speaker and microphone. There is an existing Android app available that's similar to what I need and it's name is SonicShare ([login to view URL]?t=W251bGwsMSwxLDEsImNvbS5jYW50ZmFjdG9yeS5zb25pY3NoYXJlIl0.) The code should preferably be in Monodroid ([login to view URL]).