A mobile phone is a child’s best friend, a companion who is misguiding a child’s life, ruining every moment a child progresses in their wisdom.
Can someone check this for me?
What is the context?
Why children shouldn't have mobile phones
Your sentence is fine.
Be sure to support it with solid facts.
I think you must explain why a mobile phone misguides a child's life and how it ruins his or her progress.
A mobile phone is a child’s best friend, a companion who is misguiding a child’s life, ruining every moment a child progresses in their wisdom. We should realise that a cold object that is stuck on an individual’s hands 24/7 will greatly impact their social life. Isn’t your child’s safety the most vital thing to you? Trust should not be taken at a degree...
Does it make sense?
Contradictory:
A mobile phone is a child’s best friend, a companion who is misguiding a child’s life, ruining every moment a child progresses in their wisdom.
Unexplained:
We should realise that a cold object that is stuck on an individual’s hands 24/7 will greatly impact their social life.
You have 3 different "voices" here -- 1st, 2nd, and 3rd. Pick one and stay with it.
http://thewritepractice.com/point-of-view-guide/
and
http://grammar.ccc.commnet.edu/grammar/composition/subject_object.htm