Why is there no ECG app in Australia?

Your government has to approve the ECG app.

Thanks for asking about the new ECG feature. 

Check here for availability in your region: ECG

ECG requires the following software: 

• The iPhone must have iOS 12.1.1 or later installed
• The Apple Watch must have watchOS 5.1.2 or later installed

For additional help with the ECG feature on your Apple Watch, take a look at these articles.

Heart rate notifications on your Apple Watch - Apple Support

Taking an ECG with the ECG app on Apple Watch Series 4 or later - Apple Support

If you have any other questions please reach out to our team here: https://apple.co/HeartFeatures. If you believe that you are experiencing a medical emergency, please dial your local emergency services.

Take care.