Niue is a small island in the pacific ocean with a population of 1,000. Its sole provider of cellular communications is Niue Telecom.
Niue Telecom. Edit
You can purchase a sim card at their office for $34 with $5 credit already on it.
As of now (May 2017) it is a 2G/EDGE network with 4G/LTE coming in the next few years. The frequency that the 2G/EDGE network uses is 900mhz.