Jott is a new cell phone service that converts cell phone calls to text. All you have to do is, call a specific number and leave a voice message for someone in your contact list. The message is then converted from voice to text. It can be delivered over e-mail or as a text message. This service is similar to Pinger but the conversion from voice to text makes it different. 
 
I know cell phone usage is a debated topic in schools, but try it out and see what you think. For a more detailed review, visit TechCrunch