I found this set up the other day. The text reads...
A perfect fit for SUVs, minivans, and similar vehicles with rear liftgates or hatchbacks, the DAC Explorer 2 SUV Tent lets you enjoy camping off the ground. Comfortable and convenient, the Explorer 2 is easy to set up, thanks to bungee cords equipped with plastic coated hooks that attached to your vehicles underframe. There’s no worry of bugs getting in and ruining your sleep – this DAC SUV tent’s shock cord ensures it is snug against the vehicle, and it also has a no-see-un insect screen. Other features include fold up outer door panels, two way zippers and carrying bag. Strap one to your SUV for $109.
I've never seen anything like this available in Australia. Might be a market opportunity for someone?