Seems to be here:
// Convert integer data to Char array directly
itoa(Sensor1Data, Sensor1CharMsg, 10);
then sends it out
vw_send((uint8_t *) Sensor1CharMsg , strlen( Sensor1CharMsg ));
itoa is one of those C things that you have to know about to be able to look it up:
http://www.arduino.cc/playground/Code/PrintingNumbers