Apple (NASDAQ:AAPL) has sold a ton of Macs and iPods through Amazon.com (NASDAQ:AMZN). Now it's time to return the favor.

Amazon Mobile launched this morning, a free app to give iPhone and iPod Touch owners the freedom to stroll Amazon's virtual aisles and make purchases right from their smartphones.

Uh-oh. This free app could get pretty expensive for Amazonoholics.

The neatest feature of the program is Amazon Remembers. It allows potential buyers to take snapshots of any item they see in the real world. The photo gets sent to Amazon, where a dedicated user community identifies the product or suggests an alternative.

That may sound archaic, I know. There is already at least one iPhone app that lets you take a picture of the cover of any media product -- a CD, book, or DVD -- and it uses image-recognition technology to immediately spit out the title and comparable prices. However, even that catalog is limited, given the breadth available in dozens of product categories through Amazon.

Users can simply punch UPC codes into the Amazon search box, but the Remembers feature is great for spotting objects in the wild, long after they have shed their packaging.

Either way, the delayed response is probably an unintentional feature. If it gets back to you with the product long after you've left the store, that makes going with Amazon all the easier, even if the online merchant doesn't offer the lowest price.

I decided to kick the tires. I took a snapshot of an old Canon PC980 personal copier that I figure hasn't been made in years. A few minutes later, Amazon Remembers came back with a similar Canon copier. In short, it works. I went back to Amazon.com itself to confirm that it does not sell the PC980 itself, and that was correct. There is only one third-party merchant that sells PC980 cartridges.

So what does this mean for Amazon and its 9,000 merchant partners? You have to love the timing of the app's release, just as deal-seeking shoppers are hitting the malls for their holiday shopping. Now they will have instant -- or at least nearly instant -- affirmation that they are getting the best deal out there. Amazon's merchant list includes some of the heavy hitters such as Target (NYSE:TGT) and Macy's (NYSE:M), even though Target already has its own App Store program. Retail is sure loving the iPhone. Even eBay (NASDAQ:EBAY) has a mobile platform for its auction marketplace.

Apple and Amazon are certainly not always going to be friends. They compete against one another in the digital delivery of music and video. However, during what promises to be one of the most competitive holiday shopping seasons in some time, Apple and Amazon realize that they are better friends than fighters.

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Longtime Fool contributor Rick Munarriz wonders whether he should just shut off his iPhone before he runs up a huge bill. He owns no shares in any of the companies in this story. 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, and it knows a thing or two about shopping around.