How much of a burden is this to participants?

We try to minimize the impact of the application on your life and on your phone. After all, our objective is to be able to collect enough information to succesfully perform our analysis. The application will run in the background unless you deliberately bring it to the front in order to view your activity map, for example. All collection process of the application is optimized for high energy efficiency. In addition, the application does not perform any complicated processing on the phone. The application will perform hourly uploads to two central servers whenever the phone is connected to WiFi, thus it will not incur any additional cellular data plan charges. In case you find that the application is too burdensome, you can simply uninstall it. Uninstallation directions are clearly explained on the project website.