The easiest way is to read the Temperature sensor value with some Arduino code. For example using the analog or digital inputs (just don’t use pin 10 or pin 11 as these are used by MOVI).
The MOVI can speak the value of the sensor using the SAY command. You should be able to find examples for both in the Arduino and MOVi examples.
Examples/02/Digital for a digital sensor and
Examples/03/Analog for an analog sensor
The MOVI say command is explained in detail here:
Examples/MOVI Voice Dialog Shield/Beginner/SynthesizerControl
let me know if that helped,