One of the greatest advantages to shopping online is the ability to compare prices with a quick click of the mouse. However, the advent of smartphones, which allow consumers to be online at any given moment, have taken cost comparison to a new level - now shoppers can search for ways to save online while browsing in a brick-and-mortar store.

Several applications allow consumers to enter a products code number to see the cheapest available price on the web. Should a shopper find a cheaper price listed online, they have the option to buy the item through their phone, rather than opting to buy the more costly product in the store, according to the Wall Street Journal.

"The retailer's advantage has been eroded," Greg Girard of consultancy IDC Retail Insights told the news source. "The four walls of the store have become porous." Girard's firm recently reported that approximately 45 percent of customers with smartphones had used them to compare prices while in a store.

One way that web-based retailers are reaching out to shoppers is by offering free shipping. According to the National Retail Federation, more than half of online stores will be offering no-cost shipping this holiday season.