I've used several similar services, but usually you can print out the QR code and present that instead (yes, I know: you have to have a way of receiving and pri

I've used several similar services, but usually you can print out the QR code and present that instead (yes, I know: you have to have a way of receiving and printing that, but you don't need to have a smart phone). This is also handy if you might run out of battery or network on your phone.