Beyond the obvious other pitfalls for people in the know (consumer liability is far worse, privacy is far worse with the retailers getting more data- the terms and conditions even require you to approve the collection of health related data), there are huge red flags. I just don't see it happening with sustainable "carrots" to keep consumers using the app - it's too high maintenance for it to be worth it except for massive discounts far in excess of what the merchant fees are. Not to mention one would expect the credit card companies to fight back.
The ICE agent examined the computer and saw a file labeled “2yo getting raped during diaper change,” but was unable to open it. After the suspect navigated to the encrypted portion of the hard drive, the ICE agent located and examined several videos or images that appeared to be child pornography. Id. The district court concluded that the “foregone conclusion” doctrine applied under those facts because any testimonial value derived from the act of production was already known to the Government and therefore added nothing to its case
The circumstances are different here, hence why a foregone conclusion was not found.
"Card readers? We don't need no stinking card readers." -- Peter da Silva (at the National Academy of Sciencies, 1965, in a particularly vivid fantasy)