Interesting wearable tech device in the works for a few years to simplify and make smaller, and now they are on kickstarter to sell their device. It will use gestures to communicate with your other devices.
The project on Kickstarter https://www.kickstarter.com/projects/1761670738/ring-shortcut-everything
More information http://www.humansinvent.com/#!/15643/one-ring-rule-shortcut-everything/
Example code for Xcode seems straightforward, you create the gesture and they tell it the action to perform.
var gesture_id = event.gesture_id;
href.location = '
Update: August 2015 the ring has since gone through several changes both to the materials as well as the design and many people who invested in the kickstarter campaign were not happy as they felt this was changing the product from what they signed up for. Some material changes were things like going from polished steel to plastic and having small embedded LEDs to none, and smooth surface to having a physical button sticking up on the surface. I am not aware if they were ultimately made or abandoned so there may be an opening here for a potential product. Was it ahead of it’s time? Is it not yet feasible to create such an interactive device?