Awesome

Adafruit MicroBit library

Wrapper code and examples for using microbit with arduino IDE

Included:

• BLE Serial client device for talking to Adafruit Bluefruit Connect App & Adafruit IO (Based v. heavily on Sandeep Mistry's BLE Code!)
• Adafruit_GFX compatible LED Matrix driver on Timer 2
• Internal die temperature read (but its not very good)

Check out the detailed guide here: https://learn.adafruit.com/use-micro-bit-with-arduino