Firefox OS Stumbler for Mozilla http://location.services.mozilla.com.
This application uses API only available to certified apps. So you can only install it on a developer phone. You need to enable remote debugging on your phone.
To push the application to the phone, I push it from the Firefox OS Simulator.
To create the package, use
rm stumbler.zip && zip -r stumbler.zip index.html js locales manifest.webapp style