Check out this ring, it is sure to bring out the geek in your guy. I am thinking about getting this for my husband as an accessory for his Steam Punk costume for Orycon. The price is a little steep but totally understandable considering how cool it is. Not only does it look neat, but if you go to the site you can see how the gears moves as the outside rings spin. I got the link courtesy one of the guys in our gaming group who, thankfully, felt the need to share.
The ring is made by Kinekt. They carry a couple other products as well, but it is this ring that seems to be their feature item.