Dan, from the iFly side if you wish to send NMEA data to another device you need a specific USB to Serial cable (you can get this from our store: https://ifly.adventurepilot.com/shop-t136/usb-to-serial-cable.aspx). You then enable the feed in iFly by touching Menu / Setup / NMEA Output, and configuring as needed.
As to how the Dynon or other devices need to be setup to receive the data, you will need to check with the manufacturer.
Hope this helps.