I made my daughter sign a contract for cell phones regaurding accepable cell phone use. They are all common sense to me but I thought it best to put in writing what I expected so that she can refer to it. If I ask for her phone she has to give it to me. I can read her texts, call log and open her facebook if I wanted from there. I told her that if she doesn't give me a reason I won't. If she gets in trouble I can lock any or all apps on the phone so that it requires a pin to access an app. I track where she is when I need to know. At 14 she still wants to know that I will show her respect for her privacy. The apps I use for these are:https://play.google.com/store/apps/details?id=com.domobile.applock&hl=en for locking the apps and https://play.google.com/store/apps/details?id=com.lsdroid.cerberus&hl=en for tracking
I have the ability to remotely look at text messages on her phone remotely, change her lock code, record audio remotely, look at her call log remotely but just because I can doesn't mean I always should. I have talked with her on why I need these apps on her phone and what will cause me to use the abilities to do certain things. Like with anyone communication is the key to mutual respect.