// Ensures the shake is strong enough on at least two axes before declaring it a shake.
// "Strong enough" means "greater than a client-supplied threshold" in G's.
static BOOL L0AccelerationIsShaking(UIAcceleration* last, UIAcceleration* current, double threshold) {
        double
                deltaX = fabs(last.x - current.x),
                deltaY = fabs(last.y - current.y),
                deltaZ = fabs(last.z - current.z);

        return
                (deltaX > threshold && deltaY > threshold) ||
                (deltaX > threshold && deltaZ > threshold) ||
                (deltaY > threshold && deltaZ > threshold);
}

@interface L0AppDelegate : NSObject  {
        BOOL histeresisExcited;
        UIAcceleration* lastAcceleration;
}