The device from Samsung spin-off Innomdle Lab fits any standard wristwatch and connects to Google Android smartphones.
When a phone call arrives, the wearer can accept it with a button on the band, and audio is translated into vibrations which travel up the skin.
By pushing their index finger on to the front of the ear, or tragus, the user can hear the conversation even though no one around them hears a thing.
A microphone on the watch band lets them talk to their caller, even though bystanders might think theyre just talking to themselves.
In practice, the volume is a bit low and the vibration a little strange at first, but you can hear the caller on the other end of the phone even in noisy environments.
The watch band also promises to count your steps, track your sleep, and light up when you receive text messages.
Innomdle spokesman Jai Ho Jung said the unique smartphone accessory was created by four Samsung engineers who won an in-house competition and spun their invention into a start-up company.