https://tapiriik.com/ - Syncing various on line fitness services
 

I came across this pretty cool service for syncing on line fitness services. It works with Strava, Garmin Connect, Dropbox, Runkeeper, RidewithGPS, endmondo, etc.... You can do it for free on demand or $2/yr and it will automatically try and sync them all on an hourly schedule.

I've got it set up to sync my Dropbox folder for my Cyclemeter rides, my Garmin Connect account and my Strava account. Still evaluating it, but it seems to work well.

https://tapiriik.com/

J.

For the record, you can go into Strava and tell them to import your activities from Garmin Connect (or other sources) directly, for free, with no third-party code necessary. They don't support some of the sites you mention though.