Locatrix is an Android app for tracking your location and sharing it with friends, family, and co-workers. Unlike other location-tracking tools, Locatrix preserves your privacy by only revealing city-level location every 24 hours, and by never sending raw location data off the device. The app sends location updates to our web service (node.js, hapijs, PostgreSQL). This service also provides a web interface, through which users can embed iframe or image widgets showing their city-level location and/or timezone. To avoid sending location off-device, we run nearest-neighbor lookups against a quadtree index bundled with the app.