Mesh network of cell phones when the towers go down
Klein Gilhousen, one of the founders of Qualcomm, proposed this evening at Gilder's Telecosm that cell phones be modified, if an emergency shuts down the towers, to do some basic mesh networking, not so much for voice, but for text messaging and perhaps pust-to-talk voice packets, as well as location information from their internal GPS if present.
Thus, in New Orleans, everybody would have been able to text in and out, at a battery cost to those who relay the messages to the working cell towers. Texting doesn't require continuous connectivity. In time, of course, towers would be repaired or they could be flow in on blimps or choppers.
I suggested that in fact this could be a commercially viable service, allowing people to text who are beyond the range of cell towers, possibly quite a bit beyond the range. Operators could still charge for this. (Others, more cynical, felt operators would never want stuff in phones that made them usable without the carrier.)
He also suggested some simple improvements. During Katrina, people who did get their cell phones out of town could not make calls because the databases that let them roam were "under water." The databases need to be backed up, or more simply during an emergency, switch so that unknown phones are allowed to make calls if their home system does not respond, rather than blocking them.
This requires hardware mods, unfortunately (phones today can't transmit and receive on the same bands) but otherwise is easy and could keep comms up in an emergency. A number of other cheap devices can keep power to phones.
Another person suggested phones have an ELT-like mode, where a person can enter a text message of the SOS form. Messages might indicate if the person is just advertising their location, or needs urgent help. Helicopters flying overhead could identify the phones, triangulate on them and locate all mobile owners who need rescue.