I'm a kiwi too (a director of Hiking New Zealand.com) We do remote guided small group trips around NZ. Some of us are starting to play around with digital map solutions. A good one I found is BackCountryNavigator PRO. It cost a few bucks but is excellent. You can download maps for when you are out of Internet range and your GPS works on it.
Don't use Google Maps or Apple Maps for wilderness info -- tracks etc are unreliably marked or out-of-date. excellent otherwise tho
With this tool you can do all your research at home and just buy the odd map as a back-up or for the more full on trips where you really can't afford a smart phone 'incident'. Good luck and enjoy our wonderful back-country. If you want take a look at our web site - we have a few hiking tips and ideas there too.
Reece dart is nice, plenty of other options, try and stay away from the crowded great walks huts if you are looking for solitude :-)