This project will make use of the MAX6675 Cold-Junction-Compensated K-Thermocouple-to-Digital Converter. It basically takes the millivolts produced by a standard K-type thermocouple, amplifies it, and outputs it’s temperature reading. This reading is received by a microcontroller, which then displays the reading on an LCD display. This unit will be capable of reading temperatures up 1800 degrees Fahrenheit. source

This is a good idea to take advantage of the Quartz crystal technology to implement it as crystal-based remote thermometer because of a quartz crystals have served as temperature sensors.source

This is a very good idea circuit.The circuit used to measure the precision centigrade temperature.The transmitter converting temperature sensor(voltage) to frequency which is proportional to the measured temperature. The output frequency bursts are conveyed into the mains supply cables.The receiver section counts the bursts coming from mains supply and shows the counting on three 7-segment LED displays. The least significant digit displays tenths of degree and then a 00.0 to 99.9 °C range is obtained.source

The circuit designed by Seiichi Inoue which is a Japan hobbyist.There is no MCU requires in the circuit.It used the diode as the thermo sensor to measure more than +100°C.ICL7136 of Intersil (Harris) is used for the thermometer and is measuring the change of the forward direction minute voltages of the diode by the temperature. The 3-1/2 digits liquid crystal display (SP521PR) is used for the display. The most significant digit can display only “1″.The consumption electric power of ICL7136 is very small and it is possible to operate about 3 months continuously with the a 9V batteries.source