Smartphone leader Samsung Electronics has for years been a spectator as Apple built a services “ecosystem” supporting its products. But now, as the two develop the market for mobile payments, the Korean tech giant is taking the fight to its US archrival. For Apple, offering users the ability to tap their iPhones on sales terminals to buy a coffee, snack or train ticket is a fresh revenue stream, like its iTunes music and entertainment service. The banks it works with, cough up a small charge for each transaction — reportedly 0.15 per cent in the United States. Samsung, ...