You could also get there by camel (loads of feral camels north of there) and bike (I've seen people crossing the continent on bikes). So, pretty much just rules out watercraft and large planes!
I read a really good blog series of articles about an american riding his touring bicycle from adelaide to darwin. He had to calculate his water and calories as towns were often over a days ride apart.
Quite a few cars and trucks on the highway though. You would only have to wait an hour at most for a stranger to drive by, stop and help in an emergency.