VRPose.linearAcceleration

// rendering loop for a VR scene
function drawVRScene() {
  // WebVR: Request the next frame of the animation
  vrSceneFrame = vrDisplay.requestAnimationFrame(drawVRScene);

  // Populate frameData with the data of the next frame to display
  vrDisplay.getFrameData(frameData);

  // Retrieve the linear acceleration values for use in rendering
  // curFramePose is a VRPose object
  const curFramePose = frameData.pose;
  const linAcc = curFramePose.linearAcceleration;
  const lax = linAcc[0];
  const lay = linAcc[1];
  const laz = linAcc[2];

  // render the scene
  // …

  // WebVR: submit the rendered frame to the VR display
  vrDisplay.submitFrame();
}