I love these. Basically you use a chinup bar and rather than doing regular pullups, you lay under it and do your pullups. I guess that is why they are called Australian pullups – down under?
Many exercise programs have you do these so you can build yourself up to do regular chin ups or pullups. And they do help increase your strength so you can do just that.
However, personally I do these twice a week anyway along with my regular bar work as this exercise tends to hit the lats upper back more so.
I found a good video on this. I use the Perfect Pullup so it had rotating handles which gives me both a good bicep, triceps and back workout. But here is how you can do these using a regular bar and you could even take a bar and lay it on 2 stead chairs.