Have you ever gone shopping, found something that you want to buy, and wondered if you can get it cheaper through Amazon.com (Nasdaq: AMZN)?

It happens to me all the time. As a member of Amazon's Prime member loyalty program -- paying $79 a year for free two-day shipping of any Amazon-warehoused item -- I have often held back on making a physical purchase of a new CD, video game, or consumer electronic gadget because I know that the leading online retailer will be a cheaper solution.

Well, Amazon is making it easier for owners of Apple (Nasdaq: AAPL) iPhones to do some quick comparison shopping. Yesterday's update for Amazon's App Store program includes a barcode scanning feature. Using the smartphone's front-facing camera, a product's UPC is seamlessly scanned. If Amazon carries the item, you'll have the option of buying it on the spot.

Even if you're not ready to buy, there's a huge feature that Amazon isn't really publicizing about the new scanning functionality. Opening up a product page also means checking out Amazon.com's buyer reviews for that particular product. In other words, it's not just about realizing if something can be cheaper. This update may help you decide to buy -- or not buy -- the product in question.

Nice! Stupid AT&T (NYSE: T) data plan or not, there is something to be said about spending money on a smartphone because it will save you money and heartache later. There's a promising marketing campaign for Apple and AT&T in there.

Still, what took you so long Jeff Bezos? Amazon's app has been out for a couple of years, and this is an obvious feature.

Even eBay (Nasdaq: EBAY) -- a company that has been eating Amazon's dust for years as the gap widens between Amazon's revenue and eBay's marketplace performance -- was smart enough to buy RedLaser this summer. RedLaser is one of the more popular barcode scanning apps.

Thankfully, Amazon didn't let another holiday season go by without tacking on barcode scanning. I know there will be plenty of shoppers scanning door-busters and other alleged deals come late November and early December. It's going to be another good Christmas for Amazon, as Santa Claus becomes Scan-ta Claus.   

What do you think about barcode scanning apps? Is this one more knock for conventional retailers? Share your thoughts in the comment box below.

Apple, Amazon.com, and eBay are Motley Fool Stock Advisor recommendations. Motley Fool Options has recommended a bull call spread position on eBay. The Fool owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. True to its name, The Motley Fool is made up of a motley assortment of writers and analysts, each with a unique perspective; sometimes we agree, sometimes we disagree, but we all believe in the power of learning from each other through our Foolish community.

Longtime Fool contributor Rick Munarriz has been shopping online for about as long as Amazon.com has been in business. He does not own shares in any of the stocks in this article. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.