Twitter for emergency / disaster scenarios

My company is considering using Twitter as one of many ways to send status updates and keep communication open in a disaster (earthquake, etc.). What services will we be able to provide to people without twitter accounts? For instance, can they send a message to 40404 "@username safe and well" to let us know they're OK? I've read that Twitter will create a mobile-only account in some cases, but I'm not sure if that's accurate.

Is anyone else using Twitter for disaster situations? Do you have any recommendations?