That's true. What tactile feedback could a hackysack-size ball really give though besides perceived firmness?

If the finger rings were actually more like thimbles, could they impart some texture onto a finger tip? If you were brushing over a virtual surface, could they then give a sensation of texture? Raised on a page to denote a button, etc?

I really liked the OP's article, but found it frustrating stopping short of real suggestions and predictions - great opportunity to try to forecast where things could be in 10-15 years.