Systems that would help a university to alert most of its student body at the time of an 'event' are something that the student-run Virginia Tech Planet Backsburg has just posted about on its own Twitter site.
On issues like this, one sees social media tools in a different light. The ability to send one message to an entire college campus across email, SMS and web feed in one go has its obvious benefits.
Here is the Planet Blacksburg site: http://www.planetblacksburg.com
And here is the Twitter site run by the student journalists: http://twitter.com/blacksburg