Transmitters specs from scratch

When looking for a transmitters, you need to verify some specs before you will know what kind they are looking for. 

What is application? Media?
Whats the ranged of operation?
What is the accuracy needed?
Factory calibration needed (not ranged).
***Calibration will make sure that the accuracy is correct and customer gets printed proof of that***
Tagging?

Need to fail on high or low? Can change it in the field