Hello Cathryn,
Isn't it more cost effective and natural to tune into a seismically sensitive cat, dog or bird? True, not every domestic creature is a purr-fect/grr-eat eq detector but many are. While I reside at Tahoe, I posted on another board that the NoCA-Bay Area region was going to be affected by a jolt during this time frame and I got a heads up from both my critters way before it hit.
Personally, I feel animals are more natural and more predictable than a man-made alarm. I don't believe in alarm clocks, radios or any of that stuff. Oh--another plus. Companion four-leggers don't snore either.
Cal