This was very useful 2 Christmases ago, 2013 I bought some Uggs for my mom on my dad's behalf (so they weren't on their shared credit card statement). I submitted the receipts for those and for my North Face jacket since I was keeping the receipts anyway in case a return was needed. Sure enough price on both went down and I got about $100 back total. Pretty easy. I've heard it's a way to beat doorbuster Black Friday sales.
Find the flyer, buy before the Black Friday rush, submit receipt, and when the sale is in effect after Black Friday, collect the refund.
Or so I've heard but never tried. But Price Rewind did work well the 1 time I used it.