Square credit card readers are in thousands of stores and restaurants, but the company realizes there are industries where its software isn’t appropriate. That’s why today it introduced the Square Reader SDK, which allows developers to write their own iOS or Android applications to communicate with Square’s point-of-sale machines.

This is the company’s way of getting into industries like transportation and health care.

“For the first time, iOS and Android developers can build unique checkout or point-of-sale applications like self-ordering kiosks, mobile points of sale, in-store line-busting apps, and more on top of Square’s hardware and payments ecosystem,” the company said in a statement.

Square will get its money by selling Square Readers. It offers a range of point-of-sale options, from the hand held Square Contactless and Chip Reader ($49) to the countertop Square Register Kit ($1499).

Square Reader everywhere

During testing, the company gave a select group of developers early access to the the Square Reader SDK. Among apps created is ezMetr, a digital taxi meter. This is already being used by thousands of taxi drivers to take card payments. 

And QuiqMeds built a mobile application for health-care professionals to dispense medication at the point of care so patients don’t have to visit a pharmacy.