I'm currently in the process of developing a completely open-source LTE CAT-M/NB-IoT shield for Arduino and putting together a comprehensive wiki on how to get started! The shield can be painlessly adapted to NB-IoT for many other countries and is one of the first NB-IoT Arduino shields to ever be released (if not the first *open-source* one) so don't miss out!
Check out my project on Hackaday.io!