Arduino has come up with a number of boards specifically for Internet of Things (IoT) applications. If you go to the Products page on Arduino website, you will find a separate section for IoT boards. Their prices range from $18 to $69.
The main feature that differentiates these boards from other Arduino boards (like Uno) is the presence of some connectivity onboard. For instance,
The Arduino Nano 33 IOT board has WiFi and Bluetooth connectivity.
The MKR Fox 1200 board (available in Europe only) supports the Sigfox architecture.
The MKR GSM 1400 board supports GSM.
The MKR NB 1500 supports the recently developed NBIoT protocol, and so on.
Most of these boards are compatible with Arduino IoT Cloud, which allows you to configure the values they are going to collect, generate the Arduino code automatically, and set up dashboards for visualizing the data sent by these boards. You can get the list of compatible boards here.
What's more, several of these boards are also compatible with other cloud platforms, like AWS, Azure or Google Cloud. On the product page of each board, you can find relevant tutorials. Some examples are given below −
Head on to the webpage of the product of your choice to see the available tutorials for that particular board.
These boards are, of course, facing tough competition from the Espressif boards (ESP32 and ESP8266), which are dominating the IoT landscape, and can be programmed using the Arduino IDE, and are much cheaper (ESP32, with several advanced features, like dual core operation, is priced in the $10-12 range). No wonder, Arduino IoT Cloud also provides support for ESP32 and ESP8266.