Phone ringing but it's in a pocket or bag? A prototype watch from Casio lets you silence it - by tapping your watch.

The system uses Bluetooth Low Power, a new version of the wireless technology that should appear in phones and other gadgets later this year. Casio hopes the Bluetooth watch can serve as an extension to such devices.

The prototype can also alert an incoming email and who sent it. That saves the wearer checking the phone, something that's sometimes frowned upon depending on the situation.

Information flows both ways over the Bluetooth link. With the push of a button, the watch can update time from the phone - useful for travelers because cell phones usually reset automatically to the local time.

The Casio prototype can also help find a lost cell phone. Press a button and the phone sounds an alarm, providing its within a few meters of the wearer.

Using Bluetooth Low Power, Casio says watches can stay connected to a phone 12 hours a day for 2 years before needed a new battery.

The company will open the communications standard to application makers, to encourage its adoption in smartphones and other devices.

It sees additional potential uses, such as using the watch display for information from a GPS device or sports heartbeat