Having an order that prohibits the removal of a child is worth the cost of paper. People violate court orders all day, multiple times a day. I know there is a program that will alert a parent if a passport is ISSUED for a child in a custody dispute, but I know of no such program that will alert a parent if the passport is used. Besides, if your child has dual citizenship based on mom's citizenship, it's possible for a child to be issued a passport of that country.

Best you can do is get an order ordering the surrender of the passport.