My bff's son got his first phone at 8yrs old. It was an old phone she had in a drawer, and she just added it to the plan for $10/month. The understanding was that it was her phone, for him to use, she can check it ANY time she wanted to. She programmed the "needed" numbers (her work, cell, my home and cell, different emergency numbers, his cousin and an approved friend). She gave him the phone because she had a job and he walked to school and she wanted him to phone her when he was leaving, and when he arrived on school property....and when he was leaving school, and when he got back to the neighbor's house (who was watching him). She also wanted him to have his own phone in case something happened at scouts, soccer, or if he was at his dad's house (she doesn't trust the dad but the court says he has to have visitation, so she feels better knowing her son can phone her from the bathroom or whatever if the dad got drunk or if he needed her to come get him). She allows texting, but her rule was that it was an extension to spelling and grammar homework: he can text his cousin or friend, but has to spell out all the words correctly and use correct grammar, and she checks it (again, like homework he'd enjoy). Something else she didn't tell him but gave thought to: gps on the phone if something happened and they needed help finding him.
He really wanted an iphone and he saved up his allowance and birthday/Christmas money for over a year, and now at age 10, he has his own iphone, which he bought with his own money. Same rules apply, though he does have a few more approved friends on the list now. Their data plan is shared, and unlimited because of HER job needing it to be unlimited. I don't think he has access to internet on his phone (you can specify certain things with your phone company), and he's been told not to take pictures without her approval, penalty that he loses the phone (and the money he had to save up to buy it). I don't see an issue with it at all.
I have my son (age 5) dial my mom, his dad, etc on my phone so that he can practice making calls on a regular basis. That way if there was an emergency he could use the phone with no issues. When he's about 8, I'll give him a simple basic phone, but more for emergencies. I think it would have been helpful in a couple situations I came across as a kid to be able to sneak a call, my mom had no problem being "the bad guy" and coming to get me with whatever excuse she made up, and I will provide my kids with a way to keep in touch with me as well. For those that say they grew up without a cell phone so their kids don't need one....what we DID grow up WITH was a pay phone on every corner, in every store, at every gas station, in the library, at school, everywhere. I haven't seen a pay phone in years, and the one I did see, I ran up to out of nostalgic reasons (gotta check the change slot for that lost nickel) and it was broken. So yeah---we didn't have cellphones, but the kids now don't have pay phones.