Microsoft has announced the Kinect-based Xbox Fitness. It's not a game, it's "a new online service" running on Xbox One.
The service, which features trainers who are probably famous in America such as Tony Horton, Shaun T, Jillian Michaels, Tracy Anderson and others, will be free until December 2014 for Xbox Live Gold members. It's set for launch "this holiday".
According to a post on Xbox Wire, Xbox Fitness can use Kinect to read your heart rate, "see which muscles are most engaged by measuring the power, force and transfer of weight in your body", and judge how well you're doing by tracking your balance, tempo and form.
Apparently the service will use all this to give you personalised program recommendations.
You can find out a bit more in the slightly cringe-inducing video below.
Source: Xbox Wire