Determining The Relative Position Of 2 Mobile Devices Using Ultrasound

I am considering using ultrasound (inaudible) as an option for determining the relative position of 2 mobile devices (which can be either on Android or iOS devices). There will be

Solution 1:

See related question here: Transfering data using ultrasound

I definitely think this would be possible.

As a starting point, I would look at this project and the wikipedia page for their transmission method. You would apply their processing concepts in your software audio processing code.