Yes, we have a similar app for lunches. Not clanky but it works fine.

It should help to train them for a cashless future, lol. I was in a toystore recently and I noted the check out had a contactless payment terminal and phone!

I did note myself that playing shop in the playground, my kids were unfamiliar with the process of shopping due to covid meaning I didn't take them into supermarkets much up until last year. They had no concept of change. I pay everything on phone and don't carry cash.