Mystery console error with IOHIDFamily
Solution 1:
When deploying to a real iOS device you are building for an ARM architecture, when deploying to the iOS simulator you are building for an x386 architecture.
In the latter case your app links with mach-o files present on your Mac (unless as someone suggested you only link with SDK assemblies, not native Mac ones, but this will really slow down your build and isn’t an available option anymore in recent Xcode versions I believe).
Apparently, one of these mach-o files - the IOHIDFamily extension one, which seems to be linked if GameKit.framework is linked as a library - is not specifically built for the iOS simulator. Hence, the message. As I understand this is a confirmed Apple bug and will be fixed by Apple at some point.
It is an issue with the iOS simulator only and can be safely ignored.
Solution 2:
Vinnie posted this solution
try setting the IOS Build Options: Linker options to "Link SDK assemblies only", fixed it for me
here: http://forums.xamarin.com/discussion/24656/error-running-app-after-upgrading-xamarin