The FCC was going to mandate an 8hr minimum battery backup but the Bush Admin passed it off for further study.

Most carriers have provided some kind of emergency backup but there's no telling how long it will last.

I like the "using SMS" tip. Text messages use a fraction of the bandwidth that phone calls do. You will definitely have a better chance of getting a message out via SMS.
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Safety is something that happens between your ears, not something you hold in your hands.
- Jeff Cooper