Motion sensor for game engine

I really wish the BGE had a sensor that would tell me when an object was moving, and give me a simple direction (i.e. X, Y, Z, -X, -Y, -Z). It could look and behave somewhat like the motion actuator. It would be super useful to make things happen for the AI. Like <strong>Motion[-z]<s>--</s>AND<s>--</s>Play falling animation. </strong>Or if you started sliding down a hill, it could play the running animation so the character does just glide.