I use my phone to take a picture of the price. I will continue to buy the product at the lower price until they update the tag.Interesting idea. However, I usually don't know if an item scans at a higher price until I get to the checkout. It has also been my experience that managers at the big box stores can mark down an item immediately, but they don't correct the price lower in their computer system. So, if you go back the next day, they still have the higher price in the system.
FYI, I do have a couple of degrees in computer science and a background in inventory management. So, I understand the ability to do real time updates to a computer system. But I also know that many companies have no incentive to correct prices lower when only a few old men like me complain about a price scanning higher than displayed. If they wanted, they could have a manager update the price in the system for everyone at the same time he/she marks down the item for me in the checkout line. They just don't do it.