Cumulus is a well established free Open Source flight navigation software written for glider pilots and other flight enthusiasts. This App is a port to Android of the Qt C++ application, running on Nokia's Internet Tablets N8x0 and N900.
Cumulus provides a moving map display with all the information you need to make navigation easier while flying, yet requiring a minimum of user interaction. Navigation during flight is based on the processing of GPS information delivered either by a built in GPS receiver or an external Bluetooth GPS device.
Cumulus features a full color moving map with information on terrain, airfields, airspace, (rail-) roads, water, cities and many other details. It handles waypoints, IGC logging and tasks in cooperation with KFLog, wind determination, reachable sites, final glide, sunrise and sunset calculations, airport weather stations query (METAR and TAF), flight logbook, live flight tracking via Internet and as well as automatic task point switching is also supported.
Cumulus can also process and display Flarm data, if the Android device was connected with the Flarm device via a Serial-Bluetooth adapter or an USB IOIO Uart board. The IOIO bord can also supply the Android device with power. Such adapters are offered e.g. by http://www.k6-team.de, http://www.soartronic.net or http://www.glidertools.com. Furthermore Cumulus is able to upload configuration data and task definitions to the Flarm device and to download your flights from the Flarm device.
Here are more screenshots about Cumulus to find: http://www.kflog.org/cumulus/screenshots/
If your Android device has built-in a barometric sensor, you can activate it in Cumulus and use its data as a barometric pressure altitude.
The usage of Cumulus on an Android device is only useful with a screen resolution of at least 800 x 480 pixels in landscape mode. Furthermore a screen diagonal is recommended greater than 4" otherwise you have problems to use your fingers for the operation.
One tip from me. To have a better usage of the native Cumulus part, please adapt the sizes of the GUI and Menu fonts. You can do it via the menu item Setup->General entry Look&Feel. On that page you have tow buttons to open the related font dialogs. Especially the GUI menu font should be adopted by you. Make your changes in small steps only and check the results. To get the changes full realized a restart of the program is recommended.
More information about the usage of Cumulus is to find on its web page. Here is a link to a short introduction for Android users:
Note, Cumulus is not running at Android 7 and higher version at the moment.