... well, at least the folks at Motorola think it's a good idea. Mobiledia reports that Motorola just filed a patent for a phone call notification system based on electric shocks, which should be less unintentionally distracting to people nearby than a loud vibrate (but perhaps more distracting to the user?). From the article:
The stimulator pad invention attempts to solve the problem [of distractingly loud vibrating notification] by using electric pulses to notify users. When the wearer receives an incoming call, message, or data delivery, an electric potential is placed across the electrodes and physically stimulates the body, such as areas of the epidermis and underlying muscles, alerting the wearer of the incoming call in a completely silent manner.
Interesting... although can't say I'm too excited about the idea. I think I'd prefer a distracting vibrate than a potentially miscalibrated electric shock anyday =P