Just create a script that reads your customer records, and uses the place call step to call each one back sequentially.

label get next record
read record for contact info and days until expiration
if record is not empty
     true
          place call to contact info
               success
                    play prompt your warranty is expiring in X days
                    terminate call
                    goto get next record
               failure
                    goto get next record
     false
          end

You will need some way of kicking this event off.  the easiest way is to setup an HTTP trigger on your app, then have a scheduled task hit that URL at a certain interval.