If using Skype or similar VOIP services you can pay to get a number or numbers from various parts of the world and use which one you want at any time.
I have included some info from Skype on the numbers/countries available through them and as you will see Australia is available through all types of accounts without restriction, some countries do restrict this facility to only residents of their country though if a registered company in that country they can also register :
"How do I set up a Skype Number for another country?
You can buy a Skype Number for most countries they’re available in, even if you don’t live there. Find out which countries Skype Numbers are available in.
However, some countries require proof of residence, so unless you have a valid address there, you won’t be able to get a number for that country. These countries include:
Brazil
France
Germany
The Netherlands
Switzerland
South Korea (Skype Numbers in South Korea must be purchased through our partner, Daesung.)
Verification of your registered address may vary across individual countries. The following example is for purchasing a Skype Number in Germany:
Sign in to your account.
In the Manage features section, select Skype Number, then select Get a Skype Number and follow the instructions.
In the ‘Information required for a Skype Number subscription’ page that opens, enter your valid registered address in Germany and your email details. Then check the box to confirm that you’re a resident of Germany and to accept passing your details to a German service provider.
Select Next, choose whether you want a 3-month or a 12-month Skype Number subscription, then complete the payment.
Your details will be shared and verified by the service provider and you’ll receive an email to let you know when your Skype Number has been activated."
"Skype Numbers are available to purchase in many countries and on any Skype account. Check one of the lists below for available countries by account type.
Available countries for personal accounts
Australia
Brazil*
Chile
Denmark
Estonia
Finland
France
Germany*
Hong Kong
Hungary
Ireland
Japan*
Malta
Mexico
Netherlands
New Zealand
Poland
Romania
South Africa
South Korea
Sweden
Switzerland*
United Kingdom
United States
*Unavailable for purchase with Skype Credit.
Available countries for Skype Manager accounts
Skype Numbers available for purchase through a Skype Manager account that is not registered in the United States:
Australia
Chile
Denmark
Estonia
Finland
France
Germany
Hong Kong
Hungary
Ireland
Japan
Malta
Mexico
Netherlands
New Zealand
Poland
Romania
South Africa
South Korea
Sweden
Switzerland
United Kingdom
Skype Numbers available for purchase through a Skype Manager account registered in the United States:
Australia
Chile
Denmark
Estonia
Finland
Hong Kong
Hungary
Malta
Mexico
Romania
Sweden
United Kingdom
United States
If you purchased a Skype Number through Skype Manager before September 2, 2010, from a country not listed above, you will still be able to use that Skype Number, and renew it if you want."
