Can ForeFlight and Garmin avionics talk to each other?

Yes. ForeFlight Mobile connects to several Garmin avionics systems directly or through a Flight Stream 110, 210, or 510 wireless gateway. Depending on the system, ForeFlight supports GPS, AHRS, pressure altitude, ADS-B weather, ADS-B traffic, and two-way flight plan transfer. You can learn more about ForeFlight Connect for Garmin avionics on our Connect with Garmin page. Also, for a detailed table of supported avionics, see this article: What device connect to ForeFlight?