A Welsh security company developed the tone to help shopkeepers disperse young people loitering in front of their stores while leaving adults unaffected. The company called their product the "Mosquito."
But those clever teenagers have usurped the technology and turned it into a ringtone that adults can't hear. Nice.
Still, the adults could level the playing field pretty easily. All I need to do, for example, is create a ringtone from my own voice, my kids won't hear a darn thing.