Kinect Play Fit 'Joule' monitor to track exercise on Xbox 360
An upcoming update to the Xbox 360 dashboard software will add support for a cross-application exercise tracking system as well as a new wireless heart rate monitor which will track your exercise across most Kinect games.
The heart rate monitoring device, codenamed "Joule" will accompany the new Kinect Play Fit service. Joule will obtain heart rate data and store those metrics in the cloud. Using that data, it will ensure any exercise is "within a target goal for weight loss, strength, or cross-fitness workouts".
According to sources, Joule will be compatible with most Kinect games, although it won't be required to make use of the new exercise tracking feature of Kinect Play Fit.
Unfortunately, there is no release date for Kinect Play Fit, but sources close to TheVerge have indicated that a future Xbox 360 dashboard update will introduce the system. I'd say look forward to E3 next month for more details.