I got my first phone in the middle of my freshman year of high school when my life started to pick up. After school clubs, meetings, hanging with friends, and so on, I actually needed a phone to keep contact with my parents and letting them know what was up - if I'd be be staying late, going to a friend, or to come pick me up for whatever reason.
To me, it depends on the situation of the children and the parents before one should determine if their kids actually need a phone. If the parent has a job where its hours are unstable and they can be kept back, or if the child is involved in a lot of after school programs, then I can see the need for that child to have their own cellphone in case of emergencies or something keeps either parties late (i.e the parent is stuck in work or traffic and the child's school was over half hour ago). Otherwise, I don't see the need for young kids to have a cellphone.
That being said, that's just my view of if a child has the need for their own cellphone at a young age. If a parent wants to give their child a phone just for the sake of it, then I don't think they need any overpriced cellphone or one with a load of features. Just a simple, cheap, prepaid cellphone that can receive and make calls is all the child needs in case of emergencies. Texting, internet, camera, apps - all those things aren't called for, especially when the child is so young.
On the positive outlook of it, having a cellphone can teach young kids how to be responsible while growing up. Prepaid phones with limited minutes are great so kids know to budget their time on their phones so they're not calling their friends and talking for hours. At the same time keeping it simple will also establish that a kid doesn't become addicted with any features that are uncalled for. So, in return, you can say having a phone at a young age with the right plan and need can come in useful in more than just emergency uses, bu moral lessons as well.
As for my own kids in the future, sorry for them, but they won't be getting a phone until I see they actually need one or the time calls for one. XD