With buyers developing a life-long relationship with plastic, favouring it over carrying greenbacks in their pockets, merchants who cannot afford a card-processing machine stand to lose a significant percentage of their clientele. For customers, this might mean losing out on a shopping spree. Jim McKelvey and Twitter co-founder Jack Dorsey (R) founded Square in 2009 to look for a solution and released two apps — Register and Wallet.

For the former, Square offers a plugin device called Reader that converts any smartphone into a cash register, helping it process credit and debit card payments through the app. Wallet doesn’t need an extra plugin and lets people pay using their smartphones. Square offers security features not available with a typical credit card processor: it can show the photo and location of the shopper and send receipts via e-mail. The company charges a 2.75% processing fee on each transaction, something that helped it get a $3.3 billion valuation last year.