GPS in NZ

In the UK you will almost see a GPS Satnav in every second car. They're getting as popular as mobile phones and with all the ring roads they're a must. Popular satnav models such as Tom Tom and Navman have been available in New Zealand for a number of years. I'm not sure they offer the same value that people get out of them in the UK. I can definitely see how you would want to have one if you're a courier driver. Afterall you're going to be driving to places that you are not familiar with. I can also see the value for sales people. But for every day use in NZ I can't see the need. As long as you know the main roads and can get from one district to the next you'll be fine. Would be interesting to find out how well they sell in NZ. I see them as more of a "I want that gadget" than a need. Will this area of gadgetry grow in NZ?