J.,
If you are going through a divorce, you are entering a very tough parenting time. I guess I could understand if a non custodial parent wanted the child to have a phone to contact him at any time he wanted, but it would need to be something that you supported, otherwise he would learn a great deal about splitting. Kids of divorce become very manipulative if they are given the chance to be...I have seen it first hand in my step son.
With that being said, if he needs a phone, he needs a phone, why attach it as an incentive. What will the incentive need to be next? Don't buy off your kids. Getting to school is a reponsibility, not a favor. We should not "pay" kids for meeting basic responsibilities. How about get yourself ready for school or no TV for a week? How's that for reinforcement? Not "if you do, I give...but if you don't do, I take) That makes you the parent in control.
Personally I would never give a child that age a phone, just let him call his Dad whenever he wants. Where is he going to be at age 9 if not at home with you or his dad? He really shouldn't NEED a phone if you cooperate with giving him open access to his dad.
In the end, we can give you all of our opinions, but you have to do what works for you. Just know that there may be negative health concerns related to excessive cell phone use (something about the battery being close to the brain causing tumors), and of course the concerns related to hearing loss with headphones and earbuds.
Let us know how it turns out.
D.