Nintendo soon fell silent on the topic of the Wii Vitality Sensor after announcing at E3 2009, leaving the pulse-monitoring peripheral's development progress largely a mystery. Now, the company has explained the holdup with the curious gadget, revealed in a newly-released transcript of last week's financial results briefing.

"This is a totally new type of entertainment, and there are large individual differences in the biological information of humans," Nintendo president Satoru Iwata explained. "For example, if it was acceptable that only 80% of the users thought the result was natural, then we could propose this to consumers right now. However, we are aiming for a level of quality in which 99% of consumers feel comfortable, and that is why this project is taking time to complete."

Nintendo has imagined uses for the Sensor including measuring a player's fear in a horror game and responding appropriately, or helping people to unwind with relaxation software.

"I feel that this project has a lot of interesting potential, and we would like to continue this project without giving up, but it is difficult to overcome this hurdle, so please understand that now I cannot clearly say when we will be ready to put this on the market," Iwata said.

As the Vitality Sensor's evidently still far from launching, it wouldn't be at all surprise if it ended up being released for the Wii's 2012-due successor--if the Sensor ever sees the light of day, that is.