Bookie allows you to manage bets with your friends. You can create an event to be anything and invite your friends to predict the chance the event occurs. E.g., create an event that you will get the highest score for the upcoming exam. You bet $20 at a 60% chance that will happen. Your friend bets $15 at a 40% chance. A bet is created at a 50% chance so each side puts in the same money at $15 - you win if you get the highest score, your friend wins if you dont. ($15 instead of $20 as no one can lose more than they wager). Note: No transactions are done through the app.