"I bought my child a cell phone, and next month we had a $800 cell phone bill!" - True story.

"My son lent his cell phone to his friend, and the FRIEND ran the bill through the roof!" - True story.

Most parents want to be able to stay in contact with their kids.  Cell phones are great for that.  However, they can also become more trouble than they're worth.  However, there are a lot of options to consider. Just like with their first bike, there are varying levels of "training wheels" available. 

1. Cell phone "Big-Wheel": Restricted pre-pay phones.  The phone is restricted in that the parents set what phone numbers can be called FROM the phone - and what phone numbers can call TO the phone.  And since it's pre-paid, you decide how much money to put on the phone.  Which at least removes the possibility of a $500 bill.

The Firefly (http://www.fireflymobile.com/) is probably the best example of this type of phone.  It is fairly minimal on features, but admirably serves the purpose of allowing your child to keep in touch, as well as giving you the ability to add more people that they can call as they show they can handle the responsibility.

Drawback: It does seem to have a reputation as a "kiddie phone", so once your child is out of elementary school, they might not be willing to be seen with it - depending on their peers.

2.  Cell phone "Training Wheels": An unrestricted pre-pay phone.  You can select many with all sorts of features, texting, games, music, the works.  The only restriction is that it has a set allowance of money. So they have a phone that doesn't look any different from anyone else's, but they know they have to manage their minutes so they don't run out.  Most carriers offer good rates, as well as package deals regarding texting and minutes - which can make them even cheaper.

Personally, I think Virgin Mobile (http://www.virginmobileusa.com) has the best prices/plans, as well as a good network (they use the Sprint network).  Their phones are good, but not exceptional.   Our teen has the Switch Back, and each month we add $20 to the phone - $5 goes to a block of minutes, $5 to a block of internet use, and $5 goes to a block of texting.  The remaining $5 kicks in if she goes over on any of the above. 

3. Cell phone "Mountain Bike" - Standard Plans.

I would only consider this to be an option if your teen has shown themselves to be responsible when given no limits, your plan allows you to block overages, or your teen is capable of being able to pay you when they go over. 

Overall, I'd say it's best to go with the minimum to get the job done, and leave yourself the possibility of expanding to something better when they show they can handle the responsibility.  That way you have room to grow and they feel they've accomplished something by getting something better.  That's always a better scenario than giving them an iPhone right out of the gate - and having to deal with a $800 phone bill.  You can always get them an iPod touch, and a pre-paid phone.