Last year we saw these non-functioning Casio watch rings by a Japanese toymaker:

Apparently Casio thought it was a good idea. To celebrate their 50th anniversary, this year the company is releasing this fully-functional Casio Ring Watch:

The tiny, working watch module was made possible by "the adoption of advanced metal molding technology," the company writes. "The complex shape of the Casio watch is reproduced in detail in a full metal design in the size of a ring. In addition, glass bonding technology ensures airtightness."

"The battery can be replaced, but it is waterproof for everyday use. By [utilizing] a small button battery, a digital watch with 3 buttons has been realized in a ring size. In addition, it is equipped with a 7-segment LCD. It displays not only hours, minutes, and seconds, but also date, dual time, stopwatch, etc. It comes with an emotional flashing light function that faintly flashes the light on your hand when the set time arrives."

The ring size is 10.5, but there are spacers you can use to go as low as ring size 8.

The watch will be released in December for ?19,800 (USD $128).