Just thought i'd add to the little discussion.
I do mainly all my hunting in and around the southern tablelands and as you would know it can be easy to lose your dogs from sight or sound. Which i have done on certain occasions.
I own the tracker classic brand of trackers and they are yet to fail me
Just the other week i was on a property which is full of hills and gullies typical of the southern highlands. On this occasion whilst hunting the wind had picked up to far beyond what i am comfortable hunting with due to the fact that you couldnt here a dog bark fifty metres away. So as i just decided to head home the dogs jumped headed into bracken fern down a gully. After approx 25mins i had managed to track them over 2 hills and through 2 gullies where they had a very handy boar.
So just from my point of view i think these trackers are great. It did however take a bit of time to figure out how to use the tracker effectively to use it to its full capabilities.