Simply you should use a parental control device to make sure your kids are following what you have laid out for them. To protect them from a wave of poor and harmful info that is everywhere nowadays. You see, the problem of our generation is that we have so much information that know nothing at all. I mean pointless and useless info that can be reached by our kids is very dangerous.
When it comes to apps, I prefer hardware devices over apps. Apps are good if you want to filter a single device where as hardware has the capability to filter whole networks.Still in my family I have both variants;) As for apps I use mspy to monitor my kids` messages and calls. Sometimes I check their locations and it helps me to sleep better. I highly recommend to any parent to think twice and read a lot of reviews before purchasing any parental control systems.