Apple Watch Series 6

Series 6 arrived during the pandemic, and its flagship feature suited the moment: red and infrared light sensors on the back measured blood oxygen saturation in about fifteen seconds. Apple framed it as a wellness measurement rather than a medical one.

The S6 chip was based on the A13 and ran up to 20 percent faster than its predecessor. An always-on altimeter tracked elevation changes continuously, and the always-on display became up to 2.5 times brighter outdoors. The U1 Ultra Wideband chip enabled precise device awareness and, later, digital car keys.

WatchOS 7 brought sleep tracking, hand-washing detection and Family Setup, which let a parent manage a cellular watch for a child without giving them an iPhone.