Even if you are not taking your bike overseas, the question of what goes into your luggage when you are not looking, or what comes out of it for that matter, is always an issue.
Particularly of you are carrying a boogie-board!
And, so we hear, all bags going into the USA get opened, whatever you use as a lock.
In response to this, S&S sell these natty US approved luggage locks.
S&S are the people who invented the clever mechanism for breaking bikes in two, or three, or four, making it as easy as a blink-of-an-eye to pack a tandem into a suitcase: http://www.sandsmachine.com/pack_t1.htm
The luggage locks are probably worth investing in even if you are only going to Tasmania, which is, after all 'overseas' too.