Swatch Group AG is linking up with China’s banking giants to sell a timekeeper that can make payments at retailers across the country, posing a challenge to Apple Inc.’s and Samsung Electronics Co.’s smartwatches. The timepiece will allow users to make payments at stores that have China UnionPay Co.’s point-of-sale machines, according to the Biel, Switzerland-based company which is also teaming up with Bank of Communications Co., one of China’s big-five banks.