Australia Posts own official app does tracking extremely well, added bonus if you have a parcel locker like i do (i live 40m from my parcel locker), it even throws up a QR code to scan at the parcel locker.
I used to use Deliveries for years, until they dropped AusPost, but the official AusPost app does way more than it ever did.
Give it a try
Plus getting an API key for Australia Post is beyond the scope for average users