You’ve done it again — left home without that discount dining certificate you bought. Or, you forgot to buy one, even though you’re dining at a restaurant that’s currently offering a deal. Just call up your discount certificate on your phone. Or use your phone to buy the certificate on the spot. Most daily deal services and other sources of restaurant discounts have mobile apps that allow you to call up your purchased deal or buy new certificates on the spot and show the coupon to the server on your phone. We’ve found some FREE apps you should not leave home without. Check them out in the full story on our sister site, Living on the Cheap.