RTD's and thermocouples come with NPT pipe thread. Male and female. Check
http://www.pyromation.com/All you need is an RTD (so you can extend the conductors) and a temperature controller. Since you only need the display, you will not need to concern yourself with the outputs. But you will have to set/program the sensor type.
The controller will calculate distance and resistance, so you can be accurate with extending the conductors. Use THWN or similar. You also will need a small enclosure for the controller.
Ps.....They can make the RTD cable any length you need. "Special Order"
