I gave my two a cell phone after they were able to prove to me they were able to take care of one and use it appropriately. I gave my two one mainly to keep up with them, know where they are at all times and also they can be used in case of an emergency to triangulate where they are. Kidnap victims are found this way more and more these days.
As for them being a distraction that's only if they let them plus its how they are raised too. They should know just like adults when to show respect and be courteous to others while using them or have them in your possession. For instance mine txt like crazy going to school or church but while they are there the phones stay in my car.