I can confirm that this is the case at "Albert Heijn" in the Netherlands, where you can "save" a bit of money during checkout if you were to present your loyalty card.
Thanks for your suggestion! I've created a dedicated post for the app.
Regarding your suggestions, it's already possible to use a random code: When clicking the "Enter code" button at the top, a random code is suggested to you. With a click on "Let's go", you get to the card with that random number.
If you have some experience with TypeScript and/or React, feel free to fork and contribute! I'm always happy for pull requests.
That's a great idea! I have thrown together a small web app to "emulate" the loyalty card for Payback, one of Germany's biggest loyalty card providers. Take a look here: https://apfelkompott.codeberg.page/loyalty-card-hosting/
To get started with some of the codes, I have scoured the web for images of cards, and added those to a list. (I've also provided the sources as part of the app.) You can also modify the code in the URL. As long as it's a valid EAN13 value, the bar code should render just fine.
Adding new providers/codes should be easily doable, if we had screenshot of the apps that show the design and the number format used for the code.
Let me know what you think.
PS: For the record, I am not affiliated with Payback, nor do I endorse using other people's card or code. This emulator is meant to be used with your number and your number alone.
I was not aware of this app. Thanks for mentioning it!