Currently you have to touch the screen 3 times to get the barcode display. Could you please have a shortcut on the main screen to go straight to the barcode. If you are in a hurry in the shop you don't want to stand there and tapping your phone so many times.
Once to open the app. Once to select the reward card and Once to open the barcode. Particularly if you only have one card this is troublesome. At the moment a plastic card is quicker. Perhaps you could select a default barcode option when opening the app? or select the barcode on the welcome screen?