A reciprocal arrangement would also work. My little terror will soon be at the point of having a mobile phone. My wife and I already share locations in real time. They will get the same arrangement. We can check on them, however, they can also check on our location. Moving on from this, in the future will be a negotiation, not an ultimatum.

It's also worth noting however, that a level of accountability is required with phones and social media for children. Knowing that mum or dad might go through their phone to check things makes them think about what they are doing. It is also required to make sure they don't err too badly. The key is to be open, clear and reasonable in your requirements of them. Also, never mock or belittle. To you, it might be a cute minor kids spat. To them, it's the life or death of their entire social life.

If you have a good relationship with your children, these will be a non-issues. Mutual respect (not fear) is a FAR better position to take, parenting wise.