The SmartRow App (together with the SmartRow-conversion) will turn your WaterRower into a lab grade ergometer. It will not only show you power, distance, work-per-stroke, calories etc., it will show you each force-curve, heart rate graph and much, much more! It keeps track of your workouts, and even shows you well-known fitness metrics like Watts-per-Beat and Watts-per-Kilogram. It even syncs your workout data with Apple Health.
This is the best training tool you can invest in—after hiring a coach, of course!