You might recall some of my previous posts (here and here) about the Mosquito tone - the high pitched tone that teenagers can hear but adults cannot. It was introduced as an anti-loitering feature in various European CCTV systems. The system operator could activate the annoying tone to drive away "hoodies" from the general area of a security camera in a mall, for example. Teenagers then exploited the technique against adults by making it into a ringtone for their cell (mobile) phones so that (adult) teachers could not hear the ring or text message notification in class.
The latest development is that the security implementation of the technology has undergone another evolutional generation and is being introduced into the US market. The company's Powerpoint presentation provides additional insight, even though one point it makes is entirely inaccurate - the latest version of the Mosquito system measures the ambient sound level and adjusts the level that it plays the annoying tone to be 5 dB (decibels) above the ambient, which, contrary to what the presentation claims, is not the same as being the level of a whisper. I think I understand what they were trying to get across with this point, but the way it is stated is inaccurate and misleading.
This is a controversial, yet ingenious use of technology and biology. We are sure to hear more about this in the weeks and months to come.
(Hat tip: boingboing)