17 days is a bit shortlived lol.
But, I feel it can be expanded to encompass anything you wish to do with friends where you can publicly list goals, add photos from each accomplishment etc etc with friends and family.
I don't like when apps use Facebook as a prerequisite, but I would find a way to utilize Facebook's reach without requiring it to participate. Use it as a tool - not as the foundation.
It's a concept, needs some refining - but there's promise.