I've found one actually which looks good if useful to anyone "touchOSC"Yamaha had an app like that, named "Sound Controller," but I recently heard that it's been "discontinued."I'm not sure if that means it's no longer available in the App Store, but it certainly means it won't be updated in the future to remain compatible with the latest operating system.
Fortunately, there are other apps available, such as "MIDI Designer."