Detecting calls made to InstallEventHandler

I'm currently working on a method of detecting apps that might have global access to user keystrokes. Among the currently available APIs(CGEventTap, IOHIDManager) I've also encountered [NSEvent addGlobalMonitorForEventsMatchingMask:handler], which upon further inspection seems to call into InstallEventHandler( found in HIToolbox):

extern OSStatus 
InstallEventHandler(
  EventTargetRef         inTarget,
  EventHandlerUPP        inHandler,
  ItemCount              inNumTypes,
  const EventTypeSpec *  inList,
  void *                 inUserData,
  EventHandlerRef *      outRef)

An example of this would be(requires approving the binary in System Preferences -> Accesibility):

#import <Cocoa/Cocoa.h>
#import <Carbon/Carbon.h>

//Carbon.framework/Versions/A/Frameworks/HIToolbox.framework/Versions/A/Headers/CarbonEvents.h
extern void RunApplicationEventLoop(void);

OSStatus globalKeyPress(EventHandlerCallRef nextHandler, EventRef theEvent, void *userData)
{
    NSEvent *anEvent = [NSEvent eventWithEventRef:theEvent];
    printf("%s", anEvent.characters.UTF8String);
    fflush(stdout);
    return CallNextEventHandler(nextHandler, theEvent);
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        EventTypeSpec espec = {
            .eventClass = kEventClassKeyboard,
            .eventKind = kEventRawKeyUp
        };

        EventHandlerUPP handlerFunction = NewEventHandlerUPP(globalKeyPress);
        OSStatus err = InstallEventHandler(GetEventMonitorTarget(), handlerFunction, 1, &espec, NULL, NULL);
        if (err) {
            NSLog(@"InstallEventHandler: %d", err);
        }

        RunApplicationEventLoop();
    }
    return 0;
}

The documentation for GetEventMonitorTarget states that:

The event monitor target is a special event target used to
 *    monitor user input events across all processes. When an event
 *    handler is installed on the event monitor target, the Carbon
 *    Event Manager examines the EventTypeSpec for user input event
 *    types, such as mouse-down, mouse-up, key-down, and so forth. It
 *    then requests that the WindowServer make copies of any of these
 *    events that are sent to any process, and deliver them to the
 *    current process also...

I'm guessing that some process must be managing a global list of apps registered for these events.

How can I inspect the list(ideally by registering a callback, but polling is also fine) of processes which have installed one of these global event handlers?