There’s this new device from Sonare Technologies (a part of Herman Miller) that obfuscates what you say on the phone so that passers-by or cubicle neighbors can’t hear what you’re saying. It’s marketed at cubicle workers.
To use Babble, which consists of a central device and two speakers, you record a few phrases from a script provided by Babble into the unit. It then uses those samples to obscure your voice as you speak into the telephone. It broadcasts small, separated portions of the user’s speech based on the tone and volume of his or her voice and is supposed to sound like the hum you hear in a busy place, like a shopping mall or a crowded restaurant.