This high-quality stainless steel ring is for sale at Kinektdesign.com with a lifetime warranty for a mere $165, and here is what they have to say about it:
"The patented Gear Ring is made from high quality matte stainless steel. It features micro-precision gears that turn in unison when the outer rims are spun (as can be seen in the video)."
Two words. Absolutely. Squee.
You may read a review of this ring on The Gadgeteer. This bloke did a video of his new ring, from un-boxing to lots of gratuitous rotating of the parts.
That is all!