NTT DoCoMo has unveiled a mobile telephone in the form of a wristwatch and will put the device on sale in Japan shortly.
The Wristomo device looks like a large wristwatch with a thick, firm strap that snaps around the wrist from each side.
On the end of one of these straps is the phone's microphone and on the end of the other is the earpiece. When making a call a user takes the wristphone off, unfolds the two straps and holds the device like a mobile telephone.
This makes it different from prototype wrist phones that companies such as Samsung and Motorola have shown recently. Most of those devices use a separate ear piece and microphone or require the user to speak into a microphone mounted in the wrist-worn device.
The wristphone, which is made by Japan's Seiko Instruments, has a small monochrome LCD which is used to display the time while not in use and acts as a conventional mobile telephone display while the phone functions are being used. There are nine keys for navigation and other functions on the outer side of one of the straps.
The Wristomo works on NTT DoCoMo's PHS (Personal Handyphone System) network, which is a less popular and lower-power mobile phone network than the company's PDC (Personal Digital Communications) or WCDMA (Wideband Code Division Multiple Access) networks.
The company said it is using the PHS network because its lower power has enabled the development of smaller components.
The device supports data transmission at up to 64Kbps and can access i-Mode content. Its built-in scheduler and date book will also synchronise with Microsoft's Outlook.
It weighs onty 13 grams, with talk time of 120 minutes and standby time around 200 hours.
NTT DoCoMo said the wristphone will cost about ¥50,000 (£264).