From the Government Customs Website
E-cigarettes (and/or their components) are not prohibited imports under Customs law. However, they may be subject to control under the Therapeutic Goods Act 1989 if the packaging makes a claim about any form of therapeutic benefit. See Customs.gov.au
If E-Cigarettes are detected at the border appearing to make a therapeutic claim, the goods may be referred to the Therapeutic Goods Administration (TGA). The TGA will advise whether further action is warranted, whether any claims made are classed as therapeutic, and whether seizure is appropriate under their Act.
If no therapeutic claim is made, or the TGA determines that no action is warranted, the goods are released, as they are not controlled on importation.
Websites that may be able to help you with your goals:
Fact sheet on ecigs Quit SA Gov
The official TGA website TGA Govt Site
Quit Now the Australian Government resource to help you quit smoking Quit Now
How to quit smoking guide