Re: Can't use smartphone GPS in Australia
So your dedicated GPS unit would only be exempt if you could prove that it had no means of connecting to the mobile network (e.g. for updates etc).
I don't think the courts work how you think they work.
As the ones prosecuting a criminal case (traffic offences if taken to court are criminal proceedings), the burden of proof is on the police/DPP. They are the ones that have to prove that the GPS device was or is capable of connecting to the mobile network. As a defendant, you just have to cast reasonable doubt over the prosecutions case, not proof of anything (well, unless you are attempting an affirmative defence (e.g. insanity) that is, in which case you have a burden of proof of that defence).
You'd probably need to take a high-powered lawyer and a technical expert into the courtroom with you to prove that. Good luck trying to explain that to the cop at a roadside stop.
Errm, how about just providing the product manual that lists the device's capabilities and pointing out (if it is the case) the lack of mention of mobile network connectivity in the device's specifications?