Can ForeFlight and Avidyne avionics talk to each other?

Yes. ForeFlight can connect via Wifi to Avidyne's IFD 540/440 avionics to receive GPS position and transfer flight plans to and from an Avidyne with firmware 10.2 or higher.  ForeFlight can also receive AHRS (Attitude Heading Reference System) information to enable the full Synthetic Vision display.  You can read more about our connectivity with Avidyne and other avionics providers here.