It's probably a good idea not to try and fight the law of unintended consequences. People have a natural tendency to use and recombine things in their own creative ways if the technology allows it, so very often, the street will come up with its own uses for a technology that were unimagined by its inventors or promoters.
Can you hear tones above 14kHz? I can't. Teenagers apparently can. In 2006, a British inventor Howard Stapleton exploited this facet of human nature to create a device aimed at annoying and repelling teens by emitting a high frequency pulse that adults can't hear. The device was aimed at store owners and municipal authorities, as a way to deter loitering youth. Fast forward to 2008, and it these same high frequency tones have morphed into a tool for teens to subvert adult authority! The 17kHz downloadable ringtones are exploding in popularity throughout schools, where students have discovered they can enable their phones to receive calls in class which are not audible to teachers. It's easy to see the appeal for teenagers, as these ringtones function as a pseudo-secret communication protocol, an enabling power over the adults who otherwise dominate their lives.
You can download the ringtones from sites like TeenBuzz.