Contactless payment refers to using your smartphone, smartwatch or other wearables to make digital payments in lieu of physical tender. This can be a great convenience for people that prefer to leave their wallet at home, but also spells a great danger if your device falls into the wrong hands – especially if you’re using a smartphone. Why? Because many contactless payment methods can be used on mobile phones without needing to input a passcode. In many countries, including the U.S., smartphones can be used as transportation cards for public transit.