Nice. I've actually built a startup doing exactly this a few years ago, called PriceLocal [0]. Though, unfortunately, it never really got off the ground in terms of traction.

We ended up spending I think around two years building out the functionality. Most of that time was spent arranging agreements with brick and mortar businesses to share their inventory data with us, so that we could make it function on a per-product basis. You could shop normally on Amazon, and it would drop down a banner when your product was available from a local business at or below the Amazon price. We also had it working as extensions for Chrome, Firefox, and Safari. This article had a good screenshot showing how it actually worked [1].

That was definitely one of the favorite startups I've helped build to date. It was also cool to see it featured on The Today Show [2]. I'm super bummed it didn't end up working out. Good luck to you!

[0] https://www.producthunt.com/posts/pricelocal

[1] https://www.today.com/video/new-app-promises-to-find-amazon-...

[2] https://www.cnet.com/how-to/find-local-stores-that-will-matc...

EDIT: By the way, nice name! I can't believe we didn't think of that.