Done this already
I was part of the Quake-Catcher Network for several years - small sensor mounted on the floor with my desktop analysing accelerations and sending packets to Stanford. Apparently proved the concept well, and my setup reported on several quakes, but maps of user locations showed that the network was over-represented where lots of tech people live and under-represented where most earthquakes happen. It seems that the grant ran out, and the network is no longer really active. Maybe this will replace it.