Here is a way to leverage Apple's support site and return the warranty information of an OS X system:

Download the warranty.sh script from GitHub https://github.com/rustymyers/warranty

Add a new Software item (I called mine 'Warranty Check')

Create a File Sync job to push the script to Macs (usr/local/bin is pretty safe)

 

 

This results in a Custom Inventory Return that shows the current warranty information.