If you row on a "dumb" gym erg that won't pair with your Garmin, you normally get stroke rate and HR but no split or distance. Row Estimate is a free data field that estimates your split /500m, total distance and distance per stroke from the watch's own energy-burn estimate (using the Concept2 calorie/power-pace relationship).
It writes the estimated distance into the FIT file, so Garmin Connect shows a distance chart afterward, and there's a 50–150% calibration if you know your real pace. It's an estimate, not a power meter — but it's consistent workout to workout.
Free on the Connect IQ store; feedback and device requests welcome.