You must have at least one set of BLE Nano Kit because you will need the companion board, DAPLink board, which is used to load firmware into BLE Nano from a PC.
BLE Nano is the smallest Bluetooth Low Energy System-on-Chip (SoC) development board, only 18.5 x 21mm. You could develop application using Nordic's SDK, mbed.org or our open source Arduino Library for nRF51822.
1. Arduino Library for nRF51822
2. Nordic nRF51822 BLE SDK
3. mbed's Bluetooth Low Energy API
We have prepared a video "Tutorial: RedBear BLE Nano Quick Start with Arduino".