I check in luggage earlier this year when I went to W.A...
On another trip to U.S., the check-in counter staff staff it's classified as non-hand carryable stuff...
I have put my tripod inside the checked-in luggage. No problems or whatsoever, unless you feel it is too heavy and may increase your luggauge weight. When my tripod is inside, I did not have any problem passing thru the Australian Custom. At Sydney Airport, I went to the "Things To Declare" gate and let the scanners do the job. I went there as I declared having some Chinese medicine and shoes. Read the card and you will know how strict their custom is.
If unsure, just tick you have things to declare when you are filling up the Australia Arrival Form. Lastly, "Declare or Beware"
now with the increase security,it's more safe to put tripod in lugguage.
You won't want to have eyes staring at you or people who don't dare sit together.