The advice we get in New Zealand is to get underneath something strong like a table. Sitting where I am now I could probably make it under a table in under 5 seconds.

The bigger effect maybe is that prepares you mentally for the impact, so you're already planning your next steps and aren't in quite as much surpise/panic as if you had no warning.

When things are collapsing, seconds can be the difference between life and death. Even if a system like this only saves a few extra percent of lives lost in a major earthquake, it sounds worth it to me.