A simple key remapper for Mac OS X written in Swift / Objective-C
The app uses Quartz Event Taps to intercept Key presses:
The UI allows you to gather a pair of keypresses, input and output - the program stores these pairs. Then when turned on, it detects key presses, and if the keypress matches the input it replaces it with the output. It stores the hardware independent keycode and modifier flags - so it works beyond any Cocoa events (e.g. NSEvents). The UI is all written in Swift, but the Quartz Event tap code was in objective-C (due to requiring C callbacks)