I have been unimpressed with Apples lack of parental controls. They call them restrictions. However they lack very basic parental controls such as time restrictions and location tracking.
I found this guide that outlines step by step how to control your teens iPhone: Parental Controls for iPhone Guide
It is easy to follow and they are constantly updating it as new apps and services become available. Now I will not have to waste my time buying, installing and testing apps. In fact, the iPhone Parental Controls Guide is only $10. I have wasted way more money than that on apps that either don't work at all or don't include features concerned parents, like me, need.
I had a few questions concerning my particular situation so I called their free phone support line. They were very knowledgeable and helped me to set up my teens iPhone to meet my personal parenting style. I like the fact that they don't give parenting advice or condemnation. Just tell them what you want to monitor and they will help you get there, if it is possible.
Now I can read my teen's text without their iPhone. This is soooo helpful for parents. Now I know what my teen is up to. In fact, I have kept my teen from making poor decisions by reading his texts. If you are one of those "they deserve their privacy" type parents, don't judge parents who feel the opposite way. You have know idea what they are going through. Different situations dictate different needs.
If your teen is off track you should really consider purchasing the Parental Controls for iPhone guide. You'll be glad you did.