Getting "global" mouse position in Mac OS X

NSPoint mouseLoc;
mouseLoc = [NSEvent mouseLocation]; //get current mouse position
NSLog(@"Mouse location: %f %f", mouseLoc.x, mouseLoc.y);

If you want it to continuously get the coordinates then make sure you have an NSTimer or something similar

Matt is correct, but in order to continuously get the coordinates, I believe the other option is to use event monitor provided by NSEvent. Try addGlobalMonitorForEventsMatchingMask:handler: and addLocalMonitorForEventsMatchingMask:handler:. Check NSEvent Class Reference for more detail.

Matt S. is correct that if you can use the NSEvent API to get the mouse location. However, you don't have to poll in order to continuously get coordinates. You can use a CGEventTap instead:

- (void) startEventTap {
    //eventTap is an ivar on this class of type CFMachPortRef
    eventTap = CGEventTapCreate(kCGHIDEventTap, kCGHeadInsertEventTap, kCGEventTapOptionListenOnly, kCGEventMaskForAllEvents, myCGEventCallback, NULL);
    CGEventTapEnable(eventTap, true);
}

CGEventRef myCGEventCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event, void *refcon) {
    if (type == kCGEventMouseMoved) {
        NSLog(@"%@", NSStringFromPoint([NSEvent mouseLocation]));
    }

    return event;
}

This way, your function myCGEventCallback will fire every time the mouse moves (regardless of whether your app is frontmost or not), without you having to poll for the information. Don't forget to CGEventTapEnable(eventTap, false) and CFRelease(eventTap) when you're done.

If you're not in cocoa land and an event tap is not appropriate for the situation,

CGEventRef event = CGEventCreate(nil);
CGPoint loc = CGEventGetLocation(event);
CFRelease(event);

works.