Apple has launched the fourth-generation version of its Apple Watch, featuring new hardware and software enhancements including an ECG app, the ability to detect an irregular heartbeat and a new accelerometer and gyroscope that can detect hard falls.

The ECG and atrial fibrillation capabilities will only be available for US buyers for the time being. The GPS-only Watch will be available in Australia and New Zealand from September 21, but Kiwis will have to wait until later in the year for the GPS + cellular model.