I’ve recently released a new Mac App, Garmin Backup. This is something I wrote to scratch my own itch, namely to keep copies of all the training files on my Garmin devices, automatically, when they’re plugged in for charging.
When your Garmin is plugged in, the app copies any new training files (.fit files) into a folder on your Mac. Each device keeps its files in a separate folder, even if you have more than one Garmin of the same model.
To try the app (it’s free) or for more details, go to GarminBackup.com