Say you want to buy the Jeff Goldblum DVD box set from your favorite big-box electronics store, and before you ask, no such a gem does not exist, you can open up one of a growing crop of price comparison apps on your smartphone and see if it’s selling for a lower price online. This Saturday, Amazon says if you use their comparison app, Price Check, you’ll get an extra 5% off (up to $5). From the New York Times: “The deal is the first that Amazon has offered only to mobile shoppers. They can receive the discount on up to three items in eligible categories, which include electronics, toys, music, sporting goods and DVDs.”

Always willing to get punched in the stomach as its customers enter the virtual door, Amazon tries to end up with a T.K.O. at the cash register. Come on in, here’s your 5% discount. Oh, and would you like to watch Goldblum on Blu-Ray? You would? Thanks, come again.