UIDebuggingInformationOverlay

appDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
#if DEBUG
    Class debugWindow = NSClassFromString(@"UIDebuggingInformationOverlay");
    SEL selector = NSSelectorFromString(@"prepareDebuggingOverlay");
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    [debugWindow performSelector:selector];
#pragma clang diagnostic pop
#endif
    return YES;
}

// just tap the status bar with two fingers to show the console
// http://ryanipete.com/blog/ios/swift/objective-c/uidebugginginformationoverlay/