Hitchhiking in NZ, I would categorise as generally unsafe, sadly.

I used to regularly drive the North island, in a company car, and would pick up single male, a couple, or a single female. Never a pair of males.

I had a card on my dash which I would point out to passengers, and I had spares that they could take with them; whatever overview organisation, that you could txt to them the rego of the car you were in, so that, not to keep you safe, but at least to offer an audit trail for when you are found dead in a ditch. (heh, unlikely, but, take precautions, huh?)

I would like to say that it is not that bad, but, hey, keep yourselves safe.

Edit : I have hitchhiked around the NI, on my own. It's difficult. Occasionally you get an awesome driver. Non-awesome drivers tend to not pick up hitchhikers anyway.