He highlighted the health benefits of such a device by features such as automatically notifying users you if it detects they have an elevated heart rate.
"Apple Watch has become an intelligent guardian for your health," he said. "In these areas of staying connected, exercise and monitoring your health, today we're taking Apple watch to the next level."
Apple has made the screen bigger, pushing the glass display right to the edge, giving a 30 per cent larger display while the body of the watch is actually thinner that the series 3 Apple Watch.
Apple also has a raft of new screen displays and new hardware. It has an improved speaker and microphone and is 50 per cent louder which will help certainly when engaging with Siri.
"You just won't believe the sound you get out of such a small device," Williams said.
The guts of the device received an update that promises to produce two times faster performance.
But it was new health capabilities that are the focus of the new watch series, including a new feature called Fall Detection.
"Identifying a fall may sounds like a trivial thing but it takes a lot of data," Williams said.
The watch uses an in-built accelerator and gyroscope to determine when a fall occurs, which prompts an alert on the watch to make an emergency call.
This is Apple's biggest smartwatch to date. Image/Apple.
If the device senses you are immobile for a minute after the fall it makes the emergency call for you. It also send your location to the emergency contacts on your device.
The watch will also send you notifications if you're heart rate is too low as while usually a good thing, that could be a sign of something serious, Williams.
"Apple watch can now screen your heart rate in the background and detect if users are suffering from arterial fribrilation, or an irregular heartbeat which could indicate certain health issues.
"We think this can detect a lot of people who otherwise didn't know they had an issue," Williams said.
Apple has added electrodes to the back of the watch to allow users to take an electrocardiogram or ECG.
"This is the first ECG product offered over the counter, direct to consumers," Williams said, adding that Apple received FDA approval for the capability.
Apple Watch already detected high heart rate, but can now also detect low heart rate and irregular rhythm to flag potential atrial fibrillation. And can now take an ECG on the digital crown. OK, that’s amazing. #AppleEvent
The Apple Watch series 4 will start at $699 in New Zealand. Customer will be able pre-order the device from 14 September, with retail availability starting on 21 September.
iPhone
As expected, Apple is releasing a larger size iPhone which takes the features and capabilities of last year's iPhone X and puts them in a bigger device.
Apple will release an iPhone XS with a 5.8 inch super retina OLED screen display and an iPhone XS Max which is about the size of the existing iPhone 8 Plus, but with much more screen.
The 5.8 inch 2.7 million pixels while the larger handset boasts a whopping 3.3 million pixels.
"This is the biggest display ever on an iPhone," Phil Schiller, Apple's SVP of Worldwide Marketing, said.
The front of the two iPhones are completely covered in a glass finish that is the most durable glass ever on a smartphone.
The iPhones come in three different colours: gold, silver and space grey and the device is the most dust and water resistant yet.
Apple says if you drop your phone in a pool, for example, you will be able to jump in and grab it and be confident that it will be unharmed.
But in what Apple called "the most advanced iPhone ever," the focus of the new product range was on the powerful A12 Bionic chip that will power the new iPhone range.
"What the team has done is truly, truly a breakthrough," Schiller. "The A12 bionic is the industry's first 7 nanometre chip."
Basically, the point is that the chip can process 5 trillion operations per seconds.
Apple didn't quite detail what operations we are talking about here. Either way, though, it's a pretty fast chip and will dramatically boost performance, for instance Apple says apps will launch about 30 per cent faster.
