What can I say about Kinect PlayFit? It's not a game, it's a free app. This is for those who use their Kinect as a way to exercise. There are some Kinect games that will track how many calories you burn while playing them. This app takes the data for those games and tells you the total number of calories you've burned. This data is also broken down. You can find out how many calories you've burned in each of the games you played. You can find out how many calories you've burned in a day or a week or a month.
There are achievements related to this app. The achievements can be broken down into three categories. There are the basic ones where you've burned x number of calories. There are the ones where you've burned x number of calories in a certain number of Playfit games. The finial achievements are more of a total score between you and your friends. Say the achievement asks you to burn 50,000 calories. It will add your calories and your friends calories to get that total.
In the end, this is just a way to count how many calories you've burned. It's nice for those, like me, who use their Kinect to exercise. Past that, there really isn't any purpose for this.