I teased Rob endlessly when he bought an earthquake alarm system for our apartment a few months ago. Growing up along the coast of California, I knew that you couldn't "predict" earthquakes and that your only salvation was to duck and cover. But the little alarm has actually turned out to be pretty genius.
We've had a few earthquakes in the high 3's and 4's lately and each time the alarm has worked perfectly. The secret is that the alarm helps you with those first few seconds of asking yourself, "is this just a garbage truck rolling by or do I need to go stand in a doorway?" If the alarm is ringing, it is definitely an earthquake. Since we live in a house filled with heavy art and mirror hazards, this is an important distinction.
Anyway, I have the alarm on my brain because it woke us up at 3:30 am last night for the 3.8 Santa Rosa quake. I'm a really deep sleeper and probably wouldn't wake up for anything smaller than a 6.0 if it wasn't for the alarm.