Japan already has a sophisticated early warning system that is capable of collecting readings from over 1,000 seismic sensors, but those are still not enough to prevent a massive loss of life – take for example the March 2011 earthquake, and following that, tsunami, where over 16,000 people lost their lives there.
Currently, earthquake warnings are sent via radio, television and text messages under the Area Mail Disaster Information Service, so to see it arrive on your iPhone is another way to increase your chances of being notified, and subsequently, chances of survival. Your battery life will be affected to a certain amount as well, but that’s a small price to pay when your life is at stake.