I run the ridemap.org website which is a collection of motorbike routes and I wanted a way for people to download the routes to their GPS devices. Originally I was just going to provide a downloadable GPX file but then I found that Garmin have a browser plugin that allows data to be transferred between your Garmin GPS device and your computer.
After getting it working on my website I decided to wrap it up in a WordPress plugin to make it easier to integrate in posts.
You can get the code from GitHub.
To use the plugin you will need to get a free Garmin site key from the Garmin Developer website. Then create a custom WordPress field called ‘gpx’ with your GPX data and insert the [[gpxconnect]] shortcode into your post. This will add a button to allow users to download the GPX data directly to their Garmin device.