What age is appropriate for a child to have a cell phone?

I would be hesitant to put a perfect age on getting a cell phone. I would argue that your son needs a cell phone when he is going out on his own. When he is in a situation where you need to be able to contact him, but you cannot, then would be a good time to get him a cell phone. This likely will not be until he is in middle school or even high school and has more opportunity to go out socially.