If you are going to have someday UAV buzzing around at low levels cropdusting, taking estate agents aerial fotos, doing survey work, etc
Global Hawk & Predator/Mariner aside (as they are in a league of their own) apart from cropdusting, UAVs of all shapes, sizes and styles have been operating within Oz doing such things and much more for about the last 4-5 years.
Don't tell FB.
As far as I am aware, one type being operated is capable of operating a transponder, and another ditto either now or shortly. The rest aren't so equipped for a variety of reasons - vehicle size vs. payload is one reason.