A year ago I wrote about a system to get emergency messages out over the mobile phone networks. This Emergency Management Alert (EMAlert) system is a device like a smoke/CO detector that mounts on the wall and warns people of emergency information such as severe weather, police emergencies, chemical spills, etc. It occurred to me that such a system would have been helpful in the response to the recent Boston Marathon bombing and the search for suspects. 
I talked to Alert Systems Inc founder Ken Post again to ask how the system could have helped in Boston. He explained the police could have sent out a “shelter-in-place” warning within 90 seconds. They could have drawn a polygon on a map around the geographic areas for where they wanted people to stay in place and around areas where the police would be conducting door-to-door sweeps. In areas where police were going door-to-door, they could have issued instructions for people to restrain pets and to verify it was police officers at the door before opening it. The police could have instructed people to report if they saw a certain type of car or a person matching a certain description. Immediately after the bombing they could have requested that anyone with a security camera running on a continuous loop save the recent recording and not let them be overwritten.
The system has a display that presents the warnings as text. An audible alarms alerts people when a new message comes in. The volume of the alarm can be set proportional to the level of the emergency, with an alert of an imminent threat being as loud as a smoke detector. Future versions could have a text-to-speech converter to read the messages aloud.
The receiver could also be implemented as a smartphone app. The trouble with this is the alerts would be silenced in silent mode.
Communication to the receiver is one-way. Unlike SMS messages, which have handshaking, these emergency messages are not even ACKed. The system just transmits them full-power. It doesn’t take significant bandwidth because one message goes out to all users. It does not require a SIM card, and the receiver can roam across all GSM networks.
With the user’s permission, the receiver can support ACKing, reporting when the user presses the “hush” button, and even transmitting data from a weather station. This will not be required for average users.
According to Mr. Post, no other system in use or being implemented can deliver messages targeted to specific areas. Ringdown system that generate calls to many houses at once cannot support calling an entire large neighborhood. The growth of podcasts and webcasts in place of radio and TV makes it harder to alert people by interrupting programming with an emergency message. There are initiatives to send alerts to mobile phones, but they are currently not targeted to specific areas, so users find ways to disable them to avoid be interrupted or woken by warnings that do not apply to them.
The fugitives in Boston were high-profile enough that most everyone in the area heard about them and got updates from radio and TV. The benefit from EMAlert in Boston would have been the ability to transmit customized messages to individual neighborhoods and street blocks. The system would be even more useful, according to Mr. Post, in the countless lower-profile emergencies in which not everyone in danger is aware of the emergency.
