Xiaomi has announced its 15 Ultra flagship phone at a launch event in China, where it’s going on sale starting at 6,499 yuan (around $893). The Android phone joins the company’s Xiaomi 15 and 15 Pro, which went on sale there in October 2024. It is a mostly iterative upgrade on last year’s model, but the big change is the addition of a 200-megapixel periscope camera that the company says excels in low light. The 15 series, including the Ultra, is getting an international launch this…