could benefit retailers as the competition from a host of payment providers should help drive down the fees stores pay to have transactions processed - a service currently dominated by banks and card firms Visa and MasterCard."We view merchants as overall beneficiaries of the trend toward mobile payments," said Morgan Stanley, which estimated retailers in developed countries spent up to $150 billion in 2012 to accept card payments."Expected returns should justify any incremental investments required in enabling mobile payments technology," it said in a report in January.However, it is still unclear how the retail mobile payment market will develop, with card companies and banks seen retaining a leading role in processing payments even if physical cards become obsolete.Retailers' apps might struggle to take off as customers are unlikely to be willing to use a variety of services for different stores, but the success of Starbucks Corp in combining mobile payments with promotions shows big players can succeed.U.S. RETAILERSStarbucks, the world's biggest coffee chain, launched its mobile payment and rewards app in 2011. It already has 10 million users and the firm said this month it is looking for ways to expand the program beyond its own network."The mobile payments platform has given us a higher degree of frequency and higher degree of loyalty and the question is how can we leverage that beyond our stores," Starbucks Chairman and Chief Executive Howard Schultz told CNBC television.An alternative path is also being explored in the United States, where dozens of top retailers including Wal-Mart, Target and Best Buy have announced plans to set up a joint digital wallet service - the Merchant Customer Exchange, or MCX - though no launch date has been set.Meanwhile, an attempt to create a mobile payment app universally accepted by retailers has recently launched in Germany. Yapital, owned by e-commerce firm Otto, has gone live in thousands of stores and also allows users to pay online and make peer-to-peer transfers.Yapital Chairman Nils Winkler expects just a few players to survive of the 200 initiatives now clamoring for attention in Europe, with apps tied to retailers more likely to win out than those being developed by telecom and card firms."The biggest success in this field will be retail-based. PayPal is a good example that has grown tremendously based on the retail success of eBay," he said."CLEAR BUSINESS CASE"Tesco, the world's third-largest retailer which pioneered the tracking of customer behavior with its Clubcard loyalty card two decades ago, will launch its digital wallet this year, as it also starts offering current accounts.That is part of the British supermarket chain's eventual plan to use smartphones - and its own-brand Hudl tablet computers - to allow customers to navigate stores with their devices and scan products to buy them as they shop.Sophie Albizua, co-founder of UK-based retail consultancy eNova Partnership, said her clients were ready to invest in overhauling outdated till systems to enable mobile payments. "People spent the last five to 10 years fine-tuning their websites. Now they have time to focus on something else."French supermarket group Auchan, Europe's fifth-biggest retailer, launched