There already are global gestures for VoiceOver and zooming.
You can disable/have to enable them, but only globally. I do not know whether applications can be programmed to ignore or override these behaviours.
You can disable/have to enable them, but only globally. I do not know whether applications can be programmed to ignore or override these behaviours.
These new iPad gestures cannot be overridden by your app because the OS will cancel touch events out from under your app and take them for itself when it detects the gestures are in progress.
For VoiceOver (which I've not spent a ton of time investigating yet), it seems the app doesn't even get the touch events until a VoiceOver action is "committed" in some way. VoiceOver basically overlays the entire screen with an invisible window and intercepts all touches, so it basically redefines how apps work and defines a set of its own gestures regardless of what you might have defined in your app.