"We're thrilled with how much the Apple Watch has grown in such a short time", Tim Cook told the audience during today's Gather Round keynote, which the company streamed from Steve Jobs Theater on its Cupertino campus.
Apple Watch Series 4 also has a new accelerometer and gyroscope that can detect falls.
Telsyte managing director Foad Fadaghi said Apple smartwatch " continued to dominate the Australian market", and the newest model was likely to receive a warm reception from consumers looking to upgrade from their current watch or basic fitness band.
The Apple Watch Series 4 (GPS) starts from $599 and Apple Watch Series 4 (GPS + Cellular) starts from $749 both featuring the updated design and new health capabilities.
Inside the device is the S4 chip with a dual-core 64-bit processor, which deliverers 2x faster performance. The Apple Watch can detect if your heart rate is too slow and notify you immediately.
"Apple Watch has now become an intelligent guardian for your health", said Jeff Williams, Apple's chief operating officer.
The Apple Watch, which also has 18-hour all-day battery life (including 6 hours of outdoor workout time), will be available for pre-order on September 14 and go on sale September 21. The Series 4 watch will start at $399, and go up from there depending on the model.
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Series 4 will be available in silver, gold, and space grey. Alternatively, customers can also pick up in Watch 4 in stainless steel case or a new gold stainless colour.
This new display has a 35% larger face for the smaller model, and a 32% larger face for the larger model.
Irregular heart rhythm and ECG features will be available to United States customers "later this year", Williams said. It will also send a notification if the watch detects an irregular beat that might be Atrial Fibrillation (AFib).
Apple on Wednesday introduced the Apple Watch Series 4, a brand-new version of its best-selling smartwatch. Photo: Apple The thing that might stand out the most on the Apple Watch Series 4 is how many complications fit on its bigger display. It also features ECG functionality that has been given a "De Novo" classification by the US FDA.
In other parts of the device, Apple says the crown on the Watch has been completely redesigned, and now gives you haptic feedback, so you will get a mechanical feel when you scroll or whenever you interact with the digital crown.
Cellular signals also get a boost thanks to some fiddling with the watch's new ceramic rear, so you can gabble into your watch like a nutty Power Ranger. The series 4 will be available for pre-order on Friday and will ship to consumers on September 21.
Speaking of breathing, Apple has taken its health features up a notch, including a new watch face that guides users through a deep breathing exercise.