If in an emergency you want to send a emergency message then sending a cellular phone SMS to your Twitter account is a great tool as well as long as someone is taking account of the online message i.e. 'following' the twitter feed. (assuming that they still have a Internet access i.e. Out with the emergency power outage area). There are many other alternative ways to get the message through to a more targeted audience or recipient.

For example I can send an SMS formated message showing my GPS location if required from a Java app on my Samsung handset. I can also send an SMS message to POTS landline phone (BT Text) where the service provider will create a Robo voice call of the SMS text and place the message into the landline voice mail box. Even better if the recipient end user I am trying to contact has an SMS capable land line phone handset.

Most cellular handsets can also send and receive emails quite readily as well in an emergency. Internet access (getting an IP address) is achievable via landline, ADSL, DSL, Fibre and wireless 2G and 3G access etc. Getting that IP address is what is important, whether you communicate via HTTP, VOIP, FTP, etc or the next layer above the protocol isn't really too important as long as the message recipient is up to speed on the preferred method of emergency message transmit. WAP email portals are also quite efficient for example.

What was quite shocking was that large parts of the East Coast of the USA lost not only Internet access via cable but also telephone landlines (ADSL) as well due to lack of battery or generator backup due to the inclement weather. Does you local post office still allow you to send a telegram?