In the outback areas I used to fly, I figured it would take up to 3 days for someone to get to me if I crashed. I reckon that in most of the outback you can force land and walk away, buy you need to prepare to be found and for the wait.
1. GPS EPIRB
2. Water. Everyone in the outback carries water in cars, the aeroplane should be no exception.
3. First aid / survival equipment.
4. Sat phone if you can.
5. In remote Australia you need you mobile to be on the dreaded Telstra, unless its Nth SA where Optus is better.
Always ring ahead. Never assume that fuel will be avaiulable. Most remote places only get a small number of AV GAs deliveries per year. Like the Blues Brothers, you might want fuel just before the truck arrives. If you are flying to stations call and ask if they need anything. The old Elders rule was to always take the newspapers and fresh bread. In the era of freezers, fresh bread is not so important, but the newspapers of the day and / or cut flowers are always apptreciated. Maybe some fresh fruit.
GPS works 99% of the time, but there are GPS black spots in remote areas. There will also come the day, when you get directions on the back of an envelope from a guy at a pub. The GPS is limited use then. Don't plan on simply following the magenta line. Navigation in the outback is a different beast. Its about broad position based on large features and being good about time and heading.
Don't expect winsocks. if you cant pick up wind clues from other features, then you shouldn't be there. Many times, details of airstrips will be given to you by non-pilots. You need to make your own assessment of all runways.