Strange traveller

I just purchased this app as I read that I could set time limits and that it would block my daughters IPhone. As she is only 10 she will quite happily sit on the phone all day but it was intended so that she could stay in touch with me while I am away and for her to be allowed to roam out of sight to meet her friends at their house. But when I have set limits all it will do is pop up a warning to her. Do any 10 year olds take notice of things like this? No way so I have now paid for a glorified find my iPhone app that I had and worked well anyway? Why advertise that it can be blocked if they exceed their limits if it is not possible? Am I doing this wrong or is it not possible? If it isn’t possible who can recommend an app that can as I have 2 boys that will soon be getting iPhones and I don’t want to be paying for something that doesn’t do what it was sold to do!