Currently New Zealand has one GSM ( Vodafone NZ) and one CDMA ( Telecom NZ) network. If you intend to bring a GSM phone in with you make sure it is unlocked and will accept foreign SIM cards. Prepaid SIM's cost around $35, and come with $15 credit. $10 of that requires you to fill out a questionnaire, so may take some time to come through. Coverage is fairly good and is available throughout all the major cities.
Data Networks
GRPS and 3G is available. Check out Vodafone NZ for details.
Renting a Cellphone
Vodafone offer this service. Go to VodafoneRentals for more details.
