I have written in the past about designing for web-to-mobile downloads. Some treatments are effective (ie Jetsetter) despite most being ineffective. Square has built a very simple, good looking page similar to Jetsetter's. The beauty of course is that there is one call to action and then Square can do work on the backend to send the right product information for your device. And if there is breakage in the conversion funnel, they have your mobile number and can reengage.
Smart for Square. Easy for the consumer.