I have created this Earthquake Early Warning and Monitoring System using open-source technologies. Here, I have used pressure sensor to replicate the Earthquake effect. The harder I press it, higher the value, lighter I press, lower the value. The most important aspect was to get data and send the data continuously in real-time. That's where I have used PubNub, which claims that it can send data anywhere in the world in 0.25 seconds! Yes, they have that kind of servers and infrastructure. Finally, I am using Freeboard to create the dashboard.
To give an idea of how fast this system is, in recent Nepal Earthquake, it would have given 3-5 min early warning to Kathmandu and surrounding cities as epicenter was only 70-140 Km away from them.