Wii Vitality Sensor work? According to a new patent filing, it's actually quite simple -- the unit fires infrared light right at your fingertip and reports how much passes through, just like the pulse oximeters the pros use. Games then translate the result to the unfortunately-named "relax fluid" number, which is the Vitality Sensor's equivalent of your Brain Age -- the more fluid you've got, the calmer you are. It's also allegedly sensitive enough to detect when you're breathing just by measuring the changes in your fingertip, as evidenced by a concept game where you have to closely adjust your inhaling and exhaling to get an avatar safely through a tunnel without hitting the presumably deadly walls. And now you know.