Both NB-IoT and LTE-M belong to the category of Low Power Wide Area Networks (LPWAN), which are very energy-efficient wireless transmission technologies. They enable a variety of IoT applications that focus on low cost, low energy consumption, and good building penetration. Since both standards are based on 4G/5G technology, they are extremely secure.
Unlike sensors that cannot transmit over long distances (Bluetooth, Wi-Fi), both NB-IoT and LTE-M work via Plug & Play.
E-paper displays reflect light like normal paper, so they are passive (non-luminous) displays. Texts or images are displayed permanently without the need for a maintenance voltage. Energy is only required to change the display.
Well-known examples of black/white ePaper are eBook readers like the Amazon Kindle.