MyShake app for Android.

From http://arstechnica.com/science/2016/02/help-detect-earthquakes-with-your-phone/:

Seismometers cost money to install and operate properly—but everyone with a smartphone has a passable one in their pocket. Harness enough of them and you’ve got yourself a crowdsourced earthquake-detection network that could work absolutely anywhere.

Researchers have played with similar ideas in the past but have mainly had to rely on dedicated devices, along with volunteers who were willing to connect them to their computers. But in a paper published today in Science Advances, a group led by University of California-Berkeley’s Qingkai Kong describes an Android app (available now) that’s up to the task.

Available in the Google Play store: https://play.google.com/store/apps/details?id=edu.berkeley.bsl.myshake

I installed it. Seems to be stable, although it assumes you live in California as the map always homes there and not to your location. Many people have pointed this out in the reviews.