The Petal credit card was designed for people who have had trouble getting approved for a traditional credit card. Instead of determining an applicant's credit worthiness based on their credit score, Petal looks at banking data to see what you make and the bills you pay. The card it issues comes with no fees whatsoever, although interest does accrue if you don't pay your monthly balance off.
The Petal credit card has a linked app that lets users see how much they owe and how much interest they'll accrue if they don't pay off their balance. The idea is to provide transparency and let card holders know exactly how much their debt is costing them. The Petal credit card is currently being tested in a private invite-only beta.