I'd like to suggest a plugin for allowing SMS cell phone texting. Something similar to easySMS. I don't think easySMS is actively being developed as it doesn't appear to be compatible past version 2.8 and I don't know if it is even WPMU compatible.
I can't get easySMS to send out the confirmation code on our WPMU 2.9.1 setup.
Anyways, we have several teachers who would like to text message students via their classroom blogs on homework announcements etc.