How do you integrate a custom input device with the engine input and axis mappings?

Development Programming & Scripting
6

You first define FKeys somewhere e.g.
const FKey MyoPoseRest;

and then you register the key in some initial state (e.g. when your plugin has loaded successfully) via
EKeys::AddKey(FKeyDetails(EKeysMyo::MyoPoseRest, LOCTEXT(“MyoPoseRest”, “Myo Pose Rest”), FKeyDetails::GamepadKey));

see https://github.com/getnamo/myo-ue4/blob/master/Plugins/MyoPlugin/Source/MyoPlugin/Public/MyoDelegate.h and https://github.com/getnamo/myo-ue4/blob/master/Plugins/MyoPlugin/Source/MyoPlugin/Private/FMyoPlugin.cpp for reference implementations (used in the unofficial Myo Plugin)