I've talked about this before, as have the many high school students I surround myself with daily. To refresh, here's a summary of our district's policy; one I feel is fair, and well-written, even though it's abuse has largely gone unnoticed.
Students may carry cellphones/iPods to and from school. During normal school operating hours, they must be turned off. If a cellphone is visible (or worse, audible) during instructional time, a warning will be issued. The consequence for a 2nd offense is confiscation (student picks it up at the end of the school day), and 3rd offense requires a parent to come to pick up the phone from the office.
I am all for a lift to a cellphone ban, but that said, I don't see a problem with my district's current policy. Aside from a very select few teachers using cellphones during the day for educational/business contacts relating to their positions, I don't see a reason to allow cellphones to be used during the day. While I would love students to be able to connect via Twitter, use their cameras/video features for educational use, I haven't seen or heard of anyone trying to implement something like this.
I have many students who have my cellphone number, and I have a short list of students' numbers as well. The music department relies on cellphones for inter-building communication, and communicating during after-school activities (marching band, musical, drumline, etc). I've allowed students to have their iPods/phones out during study-hall rehearsals when they've asked me to listen to a piece of music, or watch a video of them playing. I've allowed phone calls home to explain to their parents why they have a zero for the day (forgetting an instrument, for example), and I invite students to take pictures/record audio and video during performances (where legally allowed, of course).
So, for now, I'm fine with our policy, but I would be on the front lines supporting a change in policy if the use of technology warranted it.