With a static current consumption of just 200 µA, the MCP9804 Temperature Sensor from Microchip has a temperature accuracy of +/- 1° C from -40 to +125°C. Available in an 8-pin MSOP or 2 mm x 3 mm DFN package, the I²C sensor includes features such as a programmable shutdown and an alert for over- and under-temperature situations. From $1.20 each in 10,000-unit quantities.
888-MCU-MCHP, www.microchip.com 
For the Block Diagram, visit http://www.microchip.com/get/400736647685185