The photo is too blurred to for me to to see the prolegs to determine a likely family. Species in Fisera (Geometridae) and Entometa (Lasiocampidae) have erectile horns near the. head like this. I hope you can rear it to the adult moth to determine the species.
Photos of the larvae of only about 7% of the named Australian moth species have been published, i.e. the species of most caterpillars that you find CANNOT be identified. Please capture any caterpillars that you find, and rear them in captivity to discover what the adult moth looks like so that we can expand the number of identifiable caterpillars.
My dad used to grow butterflies. Had masses of food plants growing in the back yard. Pity he didn't also grow moths. Will keep an eye for them and see what I can do.