Should Cellphones be banned in schools

Lets stop for a minute and exclude the music, videos, pictures, Twitter, Facebook, apps, internet access and all other added features, just focus the phone itself, should they be banned from schools?

In a time of emergency students needs cellphones. Okay yea, the school has phones but not every class has a working phone or just have one period. And not all Teachers will let students use the phone or go to the main office, only if they feel that it is an emergency.

If my school completely bans cell phones, I think it would be completely detrimental and hazardous. 

Here's an example under my own experience : in February 2012, after coming from a field trip, began to feel very hot, my hands, face and tongue had begun to swell and my eyes turned bloodshot red. After I left the building, I at least, made it across the street, during and after I began to lose my strength (holding on to the nearest fence), I lost my sight (completely), I could hardly talk or breathe and seriously thought I was going to die, until... I USED MY CELLPHONE!!! That object saved my brown skin.

When something serious like that happens we (the students) need our phones. I don't know if this enough to persuade people about cellphones being banned but this is enough for me and parents.

 *THIS IS NOT TO SAY THAT STUDENTS SHOULD USE THEM ALL OUT AND WHILE LIKE IN CLASS BUT WHEN NECESSARY*