On a Saturday last August, Patrick Knott was in full prep mode on the range at Merion Golf Club in Ardmore, Pa., after a morning win in the club championship quarterfinals. His next match was in an hour, but he didn’t like what he was seeing from his iron shots. So he grabbed his phone, filmed his swing and sent it out for a quick look. “The feedback told me what I thought—I was pushing my hips toward the ball on the downswing,” says Knott, 40, who is a +3-handicap.