It was originally invented to repel teenagers, but now the ever-clever teens are turning it into something useful, well to them, anyway.
The product is a high-pitched tone that supposedly very few people older than 30 or so can hear, but younger people can. Store owners in England have apparently tried using it to keep crowds of kids from hanging out. Now
kids are downloading it as a ring tone and using it as a text message alert that teachers can't hear!
Of course, I can't resist the science within the matter. First of all, there seem to have been two different tones mentioned in different stories. So try listening to
them (they are on the page as #1 and #2; wait for them to load) via
The Sneeze (a very funny website!) and see if you can hear them.
Someone went a little further and posted a
set of MP3's of different frequencies so you can crudely estimate your hearing threshold. Try them. Mine was at the 16,000 Hz level.