This is the latest DS18B20 1-Wire digital temperature sensor from Maxim IC.
Reports degrees C with 9 to 12-bit precision, -55C to 125C (+/-0.5C).
Each sensor has a unique 64-Bit Serial number etched into it - allows for a huge number of sensors to be used on one data bus.
This is a wonderful part that is the corner stone of many data-logging and temperature control projects.

Features:

• Unique 1-Wire® interface requires only one port pin for communication
• Each device has a unique 64-bit serial code stored in an onboard ROM
• Multidrop capability simplifies distributed temperature sensing applications
• Requires no external components
• Can be powered from data line. Power supply range is 3.0V to 5.5V
• Measures temperatures from –55°C to +125°C (–67°F to +257°F)
• ±0.5°C accuracy from –10°C to +85°C
• Thermometer resolution is user-selectable from 9 to 12 bits
• Converts temperature to 12-bit digital word in 750ms (max.)
• User-definable nonvolatile (NV) alarm settings
• Alarm search command identifies and addresses devices whose temperature is outside of programmed limits (temperature alarm condition)
• Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive system

Documents:

• Datasheet
• mbed Example
• Bildr Tutorial