How can I start GPS track logging from an intent?
There's an open-source GPS track recording app called GPSLogger. It has shortcuts to start and stop, and also publishes the necessary intent details, so you can start and stop recording without having to interact with the phone. You can also configure it ahead of time (via the app's settings) to save files in various formats and/or upload to Dropbox, OpenStreetMap, or other sites of your choice.

I'm sure there are other apps with the same functionality.