I would write the code in python to make predictions based on user data from an API. For example twitter, I could predict RTs on a tweet based on words used. Could provide insight on best words/hashtags to use in tweets. Could create a recommendation system for people they should follow, for tweets they should RT. Or could applied to anything with an API, where we want to make predictions.
Willing to do all the python coding for the backend, to make the models. Still need business side person for marketing, and developer for the site or app. And a specific idea, or to narrow it down to one.