From Timothy Woo on Hackaday.io:
This open-source LTE shield uses SIMCOM’s SIM7000-series modules with the latest LTE CAT-M technology to allow Arduino users to painlessly connect their low-power IoT devices with the next-generation cellular technology!
NB-IoT is also available for many countries (but sadly not in the USA yet) simply by swapping out to a different SIM7000 module version. Luckily SIMCOM made it super easy to integrate this module because most of the AT commands are identical to previous version, and Adafruit has a wonderful library for their FONA 2G and 3G products. Check it out and help make this happen!
You can view the latest code and design files here on my Github page: https://github.com/botletics/NB-IoT-Shield. Note: The hardware works great but software is still under development! I plan on launching an Indiegogo campaign when I get a fully-working prototype, so stay tuned for updates!