In reference to the patent: US 2013/0208181 A1
Is this patent valid in Australia?
It is not a patent - it is an Application that was filed with US PTO and has now been abandoned. Being abandoned means the invention, if any, disclosed in the application is essentially in public domain and becomes prior art.
Status: Abandoned -- Failure to Respond to an Office Action
Go to USTPO Public PAIR at http://portal.uspto.gov/pair/PublicPair
and use the number you provided as the publication Number.
Even if it had been a patent - it is not enforceable in Australia, since it would have been granted in US. Whereas given that it is a not a patent - the disclosure in this Application can be treated as prior art for Aptent Application filed in Australia. I hope that answers your question.
However if an equivalent application was filed and granted in Australia (and is still valid) then yes that patent would be enforceable. Is it valid? Who knows. Just because a home application is abandoned in that jurisdiction - it does not mean that any other applications which derive priority are not enforceable in their own jurisdictions.