Hypersonics

[Daytona400]

they were looking at installing those for the telephones/PC speakers at my work about 5 years ago. Guess it was too expensive. Neat device tho

[Daytona400]

these guys sell a similar device for advertising.
http://www.browninnovations.com/maestroinaction1.html

When you're in the "beam" of the audio, its really neat!  The guy standing next to you can hear nothing and you can hear music/telephone calls/etc.  

These 'dome' thingys is what they were trying to sell us for cubical use:
http://www.browninnovations.com/soloinaction1.html
http://www.museumtools.com/products/secret_sound_main.htm