Don't leave your (so called) smartphone at home, you might not be able to use your credit card

 Just kidding,  This would (potentially) apply only when the phone and the card use locations are in two different countries. 

The link below has more details:

http://news.cnet.com/8301-1009_3-57619532-83/mastercard-to-boost-credit-card-security-with-smartphones