Startup Idea : credit card on phone

This may be too bold, but we are entering an age where people are putting more and more trust in their computers and mobile devices to do tasks for them, why not make a way for people to put their credit cards on the phone. New security risks would come with this type of invention, but the risk of losing your credit card is almost impossible, unless of course you loose your phone, in which case you can make it so only your finger prints can access the card. Just thought of this, it seems practical enough to work.