The Walmart app shown here has the Savings Catcher feature. If another local store has any item on your receipt for less, they pay it back to you. They do that by depositing a credit onto a Walmart e-card for you, up to $599.99 per year. You can either print out the e-card and take it into the physical store with you to shop, or you can shop online with it. It just takes a moment extra at the register and I saved $70 in 2018. I feel safe doing it because I keep zero financial information accessible on my phone.

UPDATE 11-1-18 You now have to use Walmart Pay at the register to scan the QR code when it appears on the screen. You can no longer scan the receipts at home.  IMPORTANT, do not scan your card for payment until AFTER the total and QR code appear on the screen. if you have a purchase of $29 and a Savings Catcher credit of $1.00, the screen will tell you to pay $28 more. if you scan your card ahead of time, it does catch the savings from that receipt.