ForeFlight can be connected to Flight Simulator programs running on desktop/laptop computers, or even full-size simulators. Depending on the simulator, the connection can either be via WiFi (using the "UDP" protocol) or by a wired connection to the iPad.
Simulators supported by ForeFlight Mobile include:
IMPORTANT NOTE - iOS 14: when using a Flight Simulator on an iPad or iPhone running iOS14/iPadOS14, be sure to allow "Local Network" access for that flight simulator. This can be set in APPLE SETTINGS > PRIVACY > LOCAL NETWORK > [Simulator App].