While all of above works focus on applications leveraging a single smartphone, there is another trend of leveraging a sensory data from multiple smartphones for societal scale applications. of these the most significant one so far has been detecting earthquakes from accelerometer readings from multiple smartphones. Community Sense and Response (CSR) system proposed by Faulkner. et. al. [4] leverages accelerometer sensors in smartphones for monitoring earthquakes. The ishake project designed by Jack, et. al. [9] at the University of California, Berkeley resulted in the design of a mobile client back-end server architecture that uses sensor-equipped mobile devices to sense earthquakes. In [8], accelerometers of smartphones were used to record the acceleration in real time in order to detect earthquakes