What just happened? Tim Cook and friends just announced the Apple Watch Series 6 at the company's "Time Flies" keynote event today. The wearable has a few new features that distinguish it from the previous generation, including faster silicon, an altimeter, and a blood oxygen sensor.

Apple Watch Series 6 uses Cupertino's new S6 chip. The "system-in-package" (SiP) is based on the dual-core A13 Bionic that powers the iPhone 11, so it should have better performance than the Series 5 watches. Apple claims it is 20-percent faster.

The silicon is also more power-efficient. Even with the boost in processing speed, battery life will see virtually no loss to the normal 18-hours of run time seen in earlier iterations. It will charge faster as well. Apple says the Series 6 can fully charge in an hour and a half.

Apple Watch Series 6 sports a U1 chip and "Ultra Wideband" antennas. Although Apple did not mention having anything lined up at the moment, it claims that these innovations will allow support for short-range communication applications like digital car keys.

Innovations in the always-on Retina display make it 2.5 times brighter when outdoors. So even in direct sunlight, the screen will be visible with the wrist down. Apple also added touch support when in the down position to give access to complications, notification, or even swipe gestures to change faces without waking the screen.

Series 6 now has an always-on altimeter that uses a combination of barometric pressure, GPS, and nearby WiFi networks to provide real-time ground elevation data. It is vertically accurate to one foot---a handy tool for hikers or others who might want to know their elevation at a glance.

The feature that Apple seems most proud of in Series 6 is its new blood oxygen sensors and accompanying app. On the watch's back are four new clusters of red and infrared LEDs. The light emitted is reflected and read by photodiodes. The diodes hand this data off to the Blood Oxygen app, which measures oxygen saturation (SpO2) in the blood based on color variations.

The sensors detect levels between 70-100 percent. Users can check SpO2 levels on-demand and have a reading in 15 seconds. The sensors will also work in the background when the user is inactive, including while asleep. The Health app records readings for easy tracking of blood oxygen levels over time.

The GPS-only Apple Watch Series 6 starts at $399, while the cellular + GPS version is $499. Apple is currently taking orders for both models, and units will begin shipping this Friday, September 18. Nike and Hermès models are also available as usual. Additionally, Apple introduced a budget model called Apple Watch SE. Check out our separate coverage for more information on that.