Though you might have guessed from it going dormant for years now, the Wii Vitality Sensor has officially been shelved, at least for the time being. Nintendo president Satoru Iwata said he thought the idea was interesting, but the prototypes didn't work reliably enough to bring it to market right now.
At an investor Q&A, Iwata went into detail about the Vitality Sensor's development. He said "launch has been pending because we decided that the Wii Vitality Sensor's current result is insufficient as a commercial product," and then explained what went wrong.
"After a large-scale test of a prototype inside the company, we found out that for some people the sensor did not work as expected," he said. "We wondered if we should commercialize a product which works as expected for 90 people out of 100, but not so for the other 10 people. Though I am sorry that we did not give any specific updates after this product's initial announcement, I would say that knowing that a product has a problem we should not launch it for the sole reason that we have already announced it." He said they try to launch products that work 999 out of 1,000 times, and even that isn't ideal.
This echoes similar comments from 2011, when Nintendo was apparently in the midst of trying to perfect the device. At the time, Iwata implied that it worked about 80% of the time. 90% is an improvement, but not enough to bring it to market.
The question that prompted this response was about hardware launches in general, and the investor was concerned that the Vitality Sensor going dormant might mean the same for other hardware. Iwata responded, "Though we should obviously do our best to fulfill the promises we make, we consider that we should announce a new product when we come to a stage where there will be minimal change to the contents of the announcement in the future. I hope you can understand that there is a possibility that we will postpone the launch of a new product or put it in a pending state if we determine that it does not meet the quality standards that we require."