A platform for coaches to build weight loss challenges

I see plenty of personal trainers, nutritionists and coaches selling weight loss challenges. 21 days, 60 days etc. but I am not aware of a platform to help them create and sell them. Features would include: -payments -landing page creation -community management (groups, emails) -accountability tools (gym check ins, meals pictures, kcal intake logging etc.) -Ranking members for prizes -Statistics/results (weight lost per member, pictures, before and after etc.)

Something like that.

Does anybody know any app that do this? What do you guys think of this idea?