The Xiaomi Watch S4 and Smart Band 9 Pro were launched in China on Tuesday, along with the Xiaomi 15 series. The Xiaomi Smart Band 9 Pro is the successor to the Smart Band 8 Pro and has received updated health tracking and extended battery life. The smart device is available in TPU and leather strap options. It sports a 1.74-inch 2.5D curved AMOLED display, while the Wat…