It was easy for Apple to get me to start wearing a watch again. For me to wear a ring I would have to replace my wedding band because I seriously doubt you would ever see me with more than one ring on my fingers. This would have to be one incredible product.
Let's see one ring that grows and shrinks as it needs and taps into unlimited power from afar. I gotta say as a fan of Lord of the Rings this makes me slightly uncomfortable.
I'd think the market for this would be mainly medical, not mass consumer. Go to the doctor's office, clinic, or hospital, and they slip a sensor sleeve on your finger. Lets medical staff monitor wide range of body functions in real time.