Did you know that your smartphone's accelerometer is able to sense earthquakes?14
They found out that the chip had "excellent frequency and phase response, comparable with that of some standard FBA accelerometers used in strong motion seismology", but that wasn't the be all, end all of the study. Apparently, the chip was not sensitive enough to pick up earthquakes of magnitudes of 5 or under, and also has to be set near the epicenter. However, earthquakes under 5 on Richter's scale, the ones incapable of causing severe structural damage, can still be detected by smartphone accelerometers, hence the scientists are pondering organising handset-driven emergency response networks. According to them, the main advantage of these MEMS sensors is, indeed, their common use in smartphones.
Unfortunately, the so-called earthquake detector apps for Android and iOS are merely practical jokes, so we can't recommend messing around with them, especially in real life occasions.