You can control gravity directly, yourself. Get going real fast and go over the peak of a hill. That queasy feeling in your stomach is a large lessening of gravity. You can even create a situation with no gravity in a large plane that takes a steep dive as they do when training astronauts.
However, I do agree with you that we can't just increase and decrease gravity at will. Plus, the waves of gravitational pull maybe the key to achieving "wrap speed". That wouldn't necessarily be control; but instead, a tool achieved at approaching light speed.
After all, Einstein's theory of gravitational wave theory was proven just recently on February 12, 2016. BTW, it took two large black holes coming very close together for this to be achieved. Not likely a control feature mankind would ever achieve.