I think that this would be a wonderful idea...that is if EVERYONE in the chapter participated. I know that in the chapter I advise, my girls have a sign up sheet for how many hours they worked out during the week. At the end of the month, the sister with the most hours in the gym gets a prize. So, it's not mandatory, but it is an incentive to workout.
You can't make people workout. But the world would look a lot nicer if you could!