They could have probably achieved the same thing by just having people use their wifi service? No GPS needed. The bonus is devices such as tablets could be used too. Sure it would mean needing to sign into wifi, but maybe giving people choice between wifi and GPS?
Maybe as an extension, they could even have someone walk the line, in busy locations, taking orders on a tablet, equipped with a card reader?
The wait in most coffee shops isn't the time to place your order, but to fill your order. Unless you're having just a straight pre-brewed cup of coffee, they aren't going to speed things up by using an iPad to take your order in line. If they do order favorites, for instance, you might be able to one tap your coffee order when you know you're about 5 minutes out from the store and walk right in and pick it up. If I'm already in the store, I'd rather just go to the front of the line and flirt with the cute baristas that seem to work in every coffee place in the world.