Measuring the temperature with the Raspberry Pi using the PiLogger is very easy.
The PiLogger provides a special input which is compatible with very common temperature sensors used in the heating and HVAC industry. With a jumper you can configure this input to either work with so called NTC sensors having 10 kOhm or with PTC sensors of the type PT1000.
Those two types are available in many variants, for instance as water proof tube sensor, as pipe attachable sensor or as high temperature sensor. They are offered as ready made 2 wire sensors almost with a cable length of 2m for around 10€. So they are suitable for a wide field of applications. Especially the NTC type of temperature sensors are offeres also as not enclosed pure electronic components, so they can be integrated to any custom project with special requirements.