So, here is the core problem: if you want to do this on mobile... how? You can't do the actual payment parts securely using just a web browser--if you think about it that kind of undermines the whole concept for a lot of people: you would need to host that website somewhere--and then crypto wallets that support dapps and payment processing tend to get banned by Apple, because they provide a way to bypass their cut for services using an app (even if that app is just a browser) :/.