It is becoming increasingly common to pay for goods and services using a mobile app rather than cash, check, or credit cards. In fact, consumers and businesses worldwide will make more than $1 trillion in purchases from mobile devices by 2017.

Near-Field Communications (NFC) is a technology that lets you simply tap your NFC-enabled phone to a point-of-sale terminal at checkout and pay for goods and services using radio communication. Phones have PINs to prevent unauthorized purchases and can be disabled remotely if they are lost or stolen.

Square is one of the most well-known mobile payment services. For small-business owners, it’s a simple and inexpensive way to accept credit cards. They simply plug a small card reader into a mobile device and use the Square Register app that functions as a cash register.

As a customer, you can also download the Square Wallet app to your Android or Apple iOS mobile device and link a credit or debit card. Then, when you shop at stores that accept Square payments, you don’t even have to swipe your card. Simply say your name at checkout and the cashier verifies your photo that appears on the register’s screen.

Other mobile payment options similar to Square include PayPal, Isis, Google Wallet, and GlobalPay.

Although mobile payments are convenient, they can also be a threat to being thrifty. People who pay with cash think more about the cost of a purchase, while those who pay with debit cards, credit cards, or mobile apps think more about the benefits and are often willing to pay more. Read more about the cash vs. credit dilemma.

A good balance may be in a new service just emerging called Simple (simple.com). When you use the Simple Visa debit card (and your mobile device), you can see transactions appear in your account in seconds. That way, you’ll always know how much you have available to spend. You can categorize each transaction and set spending goals. I haven’t tried it yet, but it looks like a great service.