My Ex Sociopath is tracking me

So recently I figured out that my Sociopathic Ex is tracking me via my daughters phone. After church on Sunday of this week we went to eat at a restaurant in the town my Ex lives in. Guess who shows up. Yep her and her mother along with her husband. My wife and I thought it was awful strange to pick the same restaurant so we started talking. We recalled how she has shown up or been on the road close to where we have been more than once. For instance, I was driving home from a sporting event one evening and her car zoomed by me on the highway. This was some 3-4 years ago and at that time I told my wife that I had a weird feeling she was following me. She knows where both of my kids are at all times and that is a good thing in today’s society but I also think she abuses it by tracking where my family is. Its downright creepy to me but their is no way to prove it’s going on. Maybe I should plant the phone somewhere or give it to a friend and hide and watch to see if she shows up. If she will go to this depth to stalk me what else will she do?