Six months ago nobody cared how much oxygen was in their blood. If you release a smartwatch that can’t measure SpO2 now though, nobody will give it a second look. It’s a good job, then, that Zepp’s new Z (US$349) has it onboard, alongside a 1.39in always-on AMOLED touchscreen, GPS, and built-in Alexa. The Z, which is made from a single piece of polished titanium alloy, has a 340mAh battery inside, which lasts up to two weeks with typical use or 30 days if you just use it to tell the time. Despite its serious threads it’s waterproof to 50m and can track up to 12 different sports, including running, cycling, swimming and skiing. It works with both Android and iOS devices and will also alert you to an abnormally elevated heart rate, which should come in handy if somebody tells you they’re thinking of buying a smartwatch without SpO2.