Here's how you can download the WeatherSignal app free for Android devices.
1. Go to the Google Play page for the free app WeatherSignal.
2. Tap the Install button.
WeatherSignal uses your phone's sensors to detect local atmospheric conditions. It then displays them on a weather map. You can see readouts for all of your sensors, use widgets for different conditions, save all of your data to CSV via SD card, and see the map readings of other people. There's lots of graphs and manual reports as well.