CoxVox with the SpeedCoach.
Memory functions make it easy for the crew to save speed and rate information for later review.
The Speedcoach speed display updates every stroke, giving you crew instant feedback on how effectively they are rowing. You and your crew can see if changes in technique and stroke rate are increasing the speed of the boat. You may find that concentration on quick catches is the key to efficient speed. Or, you might find that concentration on the catch generates nothing but check and slower speed. You could try stretching out lay back a few inches.