Thermocouples are a great choice for measuring the temperature at a probe, and work over a wide range; for example, the widely-used K-type thermocouple has a range of -200°C to +1350°C.
This application describes a simple thermocouple interface using uLisp:
It uses a low-cost thermocouple interface board based on a MAX6675. For more information see Thermocouple interface.