The DS18B20 is a small, accurate digital temperature sensor that can be connected to a board and used to measure temperatures from -55°C to +125°C with a measurement accuracy of ±0.5°C:
Temperature range: -67°F to +257°F (-55°C to +125°C)
Package type: 3-pin TO-92
Voltage requirements: 3 to 5.5 VDC
Communication: 1-wire single I/O pin 
 
The DS18B20 has a built-in 12-bit ADC and can be easily connected to an Arduino digital input. It also has programmable resolution stored in on-board ROM and a flexible user-definable nonvolatile (NV) alarm.