Check out SAME weather radios. They self activate after receiving a location-coded radio signal. Our Radio Shack model will wake the dead, has provision for a plug in remote speaker and it can be programmed for specific types of emergencies, while ignoring others, if you wish.

"After buying an NWR SAME receiver, you must program your county, parish or independent city or marine area into the radio. Do NOT program your radio for louder or clearer station not designated as a SAME channel. You will not receive alert. Your NWR will then alert you only of weather and other emergencies for the county(s)/ area(s) programmed. NWR receivers without the SAME capability alert for emergencies anywhere within the coverage area of the NWR transmitter, typically several counties, even though the emergency could be well away from the listener.
When an NWS office broadcasts a warning, watch or non-weather emergency, it also broadcasts a digital SAME code that may be heard as a very brief static burst, depending on the characteristics of the receiver. This SAME code contains the type of message, county(s) affected, and message expiration time.
A programmed NWR SAME receiver will turn on for that message, with the listener hearing the 1050 Hz warning alarm tone as an attention signal, followed by the broadcast message.
At the end of the broadcast message, listeners will hear a brief digital end-of-message static burst followed by a resumption of the NWR broadcast cycle.

SAME is also used in the Emergency Alert System (EAS). See EAS fact sheet for more information. Using SAME, broadcasters may receive NWR warning messages for rebroadcast in accordance with EAS rules."
http://www.weather.gov/nwr/same.htm

Jeff