nintendo wiimote with motionplus

I've been messing around a bit with combining gyro data from the motion plus module and accelerometer data from the base wiimote. I've been using a Kalman filter to merge gyro + accelerometer  for pitch and roll and this seems to work fairly well. The contribution of the gyro acts to smooth the accelerometer data, at least  for the two rotations which are not completely perpendicular to the force of gravity (pitch and roll). The accelerometer data appears to be completely useless for yaw.  The gyro data does a decent job of measuring yaw but it drifts, and the worthless accelerometer data does not help in this case. Perhaps just applying some sort of high-pass filter to the gyro yaw might allow salvaging some useful information.