Why aren’t we using our smartphones to pay for items we buy at retailers or meals we eat in restaurants? Why can’t you send money to a friend with a simple tap on an app? Europe and Asia are way ahead of us in this regard, but the US is making some progress. Joanna Stern of the Wall Street Journal tested some of the new money-moving apps and, on my America Weekend show, explained how they work and which are best. Listen to our conversation here.