What tracking apps for phones did you use and continue using?

[mueller0ne]

I speak about the apps that you install when it comes to your mind how can i spy on an iphone without installing software on the target phone or something else. Maybe you track your kid's online activity or spy on your wife/husband. If you used such apps just let us know. I would like to try. I used such apps 3 years ago and do not remember the names.