The DS18B20 is a popular temperature sensor that uses the 1-Wire protocol for communication. Recent versions of the Linux kernel include a kernel driver for this protocol, making it relatively convenient to connect one or more of these devices to a Raspberry Pi or similar device. 1-Wire devices can be daisy chained, so it is possible to connect several devices to your Pi using only a single GPIO pin, and you’ll find many articles out there that describe how to do so.