The Secure GPX Tracker allows saving single locations or whole tracks to gpx-files. You can adjust the time interval between measurements as well as the minimal accuracy of the locations to optimize battery consumption and precision to your needs.
The locations are stored in a (local) blockchain, which makes the data validatable. Manipulation of locations (GPS coordinates or date) would be detected by the app. This way you can create secure gpx-files or check if data provided by others are corrupted.
The part of the app which is responsible for the validation is OpenSource. If you are interested in more details about how the validation work, see https://github.com/shuewe87/secureGpxParser
The gpx data can be shown on a map. You have the choice between Google Map and Mapbox (OpenStreetMap) as a map provider.

The app contains two ads which can be removed by in-app-purchases.