You've heard it a hundred times but you're going to do it right! First there was Uber, then there was Airbnb, next there is <Your App Here>!!!
Create a website that works off of the idea of a Gig Economy. Aka, an app that facilitates people using services that other people on the platform provide. It must implement payments in some form. It is not necessary to use real money, however if you're interested, check out the Stripe API, a very simple way of implementing payments!