Any ideas how I could make a ring for my girlfriend?

I want to make a ring, or rather a set of rings one for me and one for my girlfriend. They should both have a kind of clicky button that when pressed by one tells the other what they need. Not really, but we can pretend that they do that. I just want them to look slick and high-tech so that it will be easy to imagine that they actually work as described. The button should have a tactile and barely audible click to it, like the iPhone’s home button. LEDs would be cool, but lets not get ahead of ourselves. I’m mainly looking for ideas for materials that would be durable, cool looking, and comfortable to wear. Bonus points for drawings!