Use-By / Used Retail Price Arbitrage

Suppose a retail chain, e.g. Walmart, had a customer loyalty card with a small display and a near-field sensor or small camera. Suppose that as a product ages on the shelf the price was reduced on a daily or hourly basis. Suppose the price change could be detected and displayed by the loyalty card. Now a shopper could "scan" a product and choose the particular can/bottle/box that had the best price at any given time. This is just the "best by date" taken to a new electronic extreme. The card could also be "loaded" at the store entrance showing "the best deals" currently available right now. Bonus discounts could be added at checkout based on the number of "best deals" chosen. This would benefit retailers as it would move older product before it expires. It would also benefit retailers if they had a better age/price policy than another store. Such a device would be easy to make using an e-display, a micro camera or near-field sensor, in a form factor about the size of a credit card. Indeed, it could be a Walmart-branded Visa credit card. The current credit cards already carry a processor capable of handling this. I'm pretty sure eInk can be configured into a credit card format, using minimal, externally supplied rechargeable power. Surely someone can make this happen.