More consumers are using mobile devices today than ever to make purchases both in stores and online. In fact, U.S. retail sales from smartphones and tablets will hit $39 billion this year, which is up 56% from a year ago, according to data from eMarketer. Taking this a step further, Andrew Lipsman, VP of industry analysis at comScore, says mobile purchases now account for $1 out of every $10 spent online. This creates a clear opportunity for retailers in the fast-growing mobile commerce, or m-commerce, space.

With the all-important holiday shopping season around the corner, let's take a closer look at two retailers betting on mobile apps to boost holiday sales this year.

Brick and click
Smartphones accounted for as much as 63% of the $10.6 billion in m-commerce sales during the first half of 2013, according to comScore. This means that the best-selling stores this holiday season will likely be those with a strong presence on smartphones. Target (TGT 0.54%) and Amazon.com (AMZN -1.65%) are particularly well positioned to capitalize on this emerging sales channel.

Target's says its My Kind of Holiday campaign is the company's "most digitally enabled effort" to date. The initiative hits Target stores this week and will run across all channels, including radio, TV, in-store, catalogs, digital, and social media. Cartwheel by Target along with the Target's regular mobile app should also help drive sales for the discounter.

The company's Cartwheel app for iPhone and Android devices will let users unlock mobile coupons and take advantage of special deals offering 30% to 50% off gifts throughout the holiday rush. Target even integrates this mobile savings app with the in-store experience. Customers can use their smartphones to scan a unique Cartwheel barcode at checkout.

Source: Target app screenshot

Amazon also has a compelling suite of digital offerings in time for the holidays. For starters, Amazon's mobile apps and mobile website now feature a carefully curated 2013 Holiday Toy List. The e-tailer is also offering limited-time lightning deals both online and through its mobile apps. Similar to Target's timely Cartwheel deals, guests can get as much as 50% off select items with Amazon's lightning promotions.

Last year, Amazon customers bought more than one toy per second via mobile devices, according to the company. And this year could be even sweeter for the world's biggest online seller, thanks to Amazon's new digital initiatives. As you can see in the chart below, Amazon is currently the leader when it comes to mobile traffic. Meanwhile, Target rounds out the top five, coming in behind eBay, Wal-Mart, and Apple.com.

Source: comScore. 

To really drive the point home, comScore suggests that roughly 35% of these retailers' average monthly audience comes exclusively from mobile. Moreover, "What this means is that retailers who do not (at a minimum) optimize their mobile browsing experience or introduce mobile apps are effectively turning away a third of their potential customers," according to Lipsman.

All of this data points to one thing: 'Tis the season to shop on your mobile device.