Can my Ex- gives my child a phone watch "tracking device" when I am visiting my son?

Interesting question. If the GPS is neither specifically allowed nor prohibited, there is no clear answer. I doubt your order requires you to inform her of each and every location you take the child. What is important is that she have communication with the child (and that need not be constant). For that she has your phone number. I recommend temporarily disabling the GPS on the phone. In my opinion, neither of you is violating the order.

I agree with Mr. Mullaney's response 100%. You may wish to review your mediated agreement to see if there is a means of addressing such disagreements over parenting issues other than going back to court for clarification. I usually include provisions for referring disputes to a "Parenting Coordinator" or returning to a mediator should the parties not be able to agree on a parenting issue. Both cost money, but less than returning to court. Please let us know if these answers are helpful by hitting the helpful button.