Minor children who are under your roof do not have a right to privacy. It is a privilege.
Spouses often use surveillance technology on other spouses. You seem to think that this has only occurred with high technology. Maybe you are forgetting that in the past low technology tracking occurred.
Perhaps you forgot about the hairdresser salons where wives could keep track of gossip. Perhaps you forgot that when we lived in a more community-minded society people would call parents when they saw their kid was in a weird place or doing something they shouldn't be doing - and parents wouldn't be offended. People did and still do hire private detectives to check out what others are doing, especially if that person is acting funny or out of character, or they think they are lying.
You seem to have a problem with parents wanting to know if they can actually trust their child. If she had been trustworthy and doing the right thing, nothing would have come of it and this story would not exist because doing the right thing isn't news.
Actually, your comments, and your moniker, indicate that you have doubts trusting your children.