This is my first time hearing the term 'ultrasound tracking'. This is another good reason to avoid apps which require access to your microphone for no apparent reason.
I think I'm going to invent a device that puts out a sound that cancels ubeacons. Heck, I might just write some software and unleash it to an unsuspecting world and drown out all subsonic frequencies.
very interesting thing, but the reliability is big challenge.