Nintendo announced the Wii Vitality Sensor for their Nintendo Wii platform. The device looks similar to a heart beat monitor that hospitals use which attaches to the tip of your finger.
The purpose of the device is to keep track of the players current stress level to help relax them. Nintendo didn’t show any tech demos or anything else besides informing the world that such a device exists. So… there you have it. For that one guy who wished your Wii could track your heart rate, it seems Nintendo listened to just you during this particular E3 announcement.