Hans Jørgen Grimstad writes about nRF52840:
If you are working on anything IoT-related, the first thing you will need is connectivity.
For anything even moderately distributed that also has to run on batteries, this translates to incorporating hardware that enables you to send and receive messages using low-power radio access technologies like LTE-M or NB-IoT.
Since these are mobile network technologies, you will also need a SIM card and subscription.
Jared Wolff has designed a really nice and small IoT development board, namely the nRF9160 Feather. It measures 21x53mm in size without the antennas and should be easy to incorporate in any IoT prototype.