1. Apple on Tuesday unveiled the Apple Watch Series 6 smartwatch that can measure the user's blood oxygen level from the wrist in 15 seconds. 2. The sensor uses green, red and infrared LEDs, in addition to the four photodiodes on the Apple Watch’s back crystal, to measure the light reflected back from blood. 3. Using an algorithm built into the Blood Oxygen app, the watch then measures your blood oxygen level between 70% to 100%. 4. These measurements are especially important for people with chronic conditions like asthma, heart disease and chronic obstructive pulmonary disease. 5. Apple plans to conduct health studies around asthma, heart disease and COVID-19 using this new blood oxygen measurement capability.