If you're thinking of travelling overseas any time soon, go and get your passport, scan it and insert a digital copy onto your iPad. It might just save you if you happen to lose the real thing, as a Canadian man discovered over Christmas.
Montreal resident Martin Reisch was about two hours from home, heading to the States to drop off some Christmas presents to friends when he realised he'd left his passport at home. Rather than turn back, he decided to try and get through using a digital copy stored on his iPad. Even though the border official was slightly annoyed, he let him through. Even more interesting is that the Canadian officials also let him through on the way back.
It's important to note that Reisch was making a land crossing, so there wasn't quite the same level of invasive security to check he wasn't a terrorist. He also had his drivers license with him to help confirm his identity. Even though he made it through, the chances of the same thing happening again are slight, especially for Aussies arriving from a long-haul flight.
Still, probably best to have a copy stored digitally anyway. Just in case.