Change the text color of the status bar on iPhone and iPad (works for iOS 7 - iOS 12)

ios7_statusbar_textcolor

/// sets the status bar text color. returns YES on success. currently, this only
/// works in iOS 7. It uses undocumented, inofficial APIs.
BOOL setStatusBarColor(UIColor *color)
{
    id statusBarWindow = [[UIApplication sharedApplication] valueForKey:@"statusBarWindow"];
    id statusBar = [statusBarWindow valueForKey:@"statusBar"];
    
    SEL setForegroundColor_sel = NSSelectorFromString(@"setForegroundColor:");
    if([statusBar respondsToSelector:setForegroundColor_sel]) {
        // iOS 7+
        [statusBar performSelector:setForegroundColor_sel withObject:color];
        return YES;
    } else {
        return NO;
    }
}

Disclaimer: please note that including this code into your app will probably prevent it from being approved by the app store. Don't say I didn't warn you!

this no longer works with iOS 13 :-(
In iOS 13, the status bar is rendered by a system process and we therefore cannot "customize" it anymore.