Bed, Bathrobe and Beyond
Hotels may also create items that will make a visit more of an "experience," Professor Verma said, and those products need to be closely tied to the brand image. A luxury hotel may be able to sell bath salts, for example, while a hotel with a healthy-living theme may choose to sell yoga mats.

Westin Hotels has been particularly successful with its line of Heavenly branded products, including robes, bedding, lotions and shampoos. Since 1999, according to the company, it has sold more than 100,000 of its Heavenly Bed mattresses, and 250,000 pillows identical to the ones it offers in its hotel rooms. It sells the products through its website and partners, including Nordstrom, Amazon and Pottery Barn stores.

While the product sales have been growing for the industry as a whole over the last five years, it is difficult to determine their success because most brands do not release sales figures.

One fan of Westin's products is Dr. Vincent Casingal of Charlotte, N.C. When he was training to be a transplant surgeon and living on a budget, a stay at the Westin hotel in Pittsburgh was a luxury, and he promised himself he would one day buy a bed like the one he slept in there. For his 40th birthday recently, his wife, Allyson, bought the mattress, box spring, pillows, sheets and duvet cover from Westin's line.

Brian Povinelli, global brand leader of Westin, said the objective of the Heavenly line of products was to let guests "take a piece of the brand home with them," so they thought about the hotel after they had checked out. It is important to keep the product line "tightly curated" he said, with the goal of recreating some of the hotel experience at home.

The hotel chain recently opened a small store inside the Westin Gaslamp Quarter hotel in San Diego to showcase its home products. Many new Westin Hotels and lobby renovations will include the retail concept, according to the company. (Read more: Westin Debuts Indoor Vertical Gardens, Upgraded Lobbies)

Interest in the Westin's Heavenly products is growing in Asia and Europe, where customers can currently buy items only at the hotels, Mr. Povinelli said. So Starwood Hotels and Resorts, which owns Westin, is building e-commerce platforms to make it easier for guests to buy those items. Still, Starwood is a multibillion-dollar company, Mr. Povinelli said, so the products do not supply significant revenues.

Other hotels recreate different experiences. Guests who loved the smell of the Fullerton Bay Hotel in Singapore can buy a $70 scent diffuser, modeled after the scent wafting through the hotel lobby. Customers at the Plaza Hotel in New York can buy the original guest room doorknobs for $550. The door knobs have been replaced with modern replicas so they can operate with electronic key cards.

Some hotels sell specialty foods related to the property. The Merrion Hotel in Dublin created a line including jams and other spreads in response to customer requests to take home items they had sampled in the hotel. At the Baur au Lac hotel in Zurich, hotel-branded chocolate bars are for sale. The objective is to "stay in our guest's mind after departure," said the owner, Andrea Kracht. In addition, he said, "People automatically combine Switzerland with chocolate and the other way around."

The special items can sometimes make a difference. Ms. Casingal, who bought her husband the Westin bed set, said she loved the bath products and robe at the Loews Miami Beach hotel when she stayed there this January. So when it was time to choose a hotel in New York this summer, she chose Loews again. "The location was good, the price was right and I knew I'd be lounging in that robe," she said.

Laurence S. Geller, the founder and chief executive of Strategic Hotels and Resorts, said that branded bedding, foods or keepsakes did not significantly affect the bottom line at most hotels, so managers needed to think carefully before creating their own products. "It is hard to compete against large consumer companies that have spent billions building their brand image," Mr. Geller said, "and there is a great deal of overhead to create, distribute and account for any hotel-branded product."

The special products also cannot outweigh the basics, he said. "The pillow may be spectacular, but if the hotel is off location and costs more, no one's going to stay there just for the pillow."

If a hotel brands something, it should be for a good reason, he said. Mr. Geller saw that the Ritz-Carlton in Half Moon Bay, Calif., which is owned by Strategic Hotels, catered to customers ages 50 and older and needed to reach out to the younger demographic of corporate meeting planners. He added a wine tasting room there called ENO, to provide a hipper vibe. "Hotels are expensive to run so we need to maximize revenue per square foot," Mr. Geller said, "and that includes the rooms, grounds, roof, walls, meeting areas and what we choose to sell in our retail spaces."