All things aside, SMS is probably the worst possible way to inform anyone in any case of emergency. SMSes are hitchhiking on the back of the carrier signal and have absolutely the lowest priority of any form of cellular communication (yes, staying on 3G and connected to a non-relayed IM is actually better than the SMS), and they are relayed routinely on high network loads. They even don't have guaranteed delivery.

Pagers (in their original form) are actually way better than the SMS for a quick message delivery.