I dont find much issue with counting lengths. Over time you get a reasonable assurance about the accurcy of length counting by comparing it with your expected lap time. For longer swims I move a water bottle along one tile every 16/20 lengths depending on distance.
Stroke count is one of the things that gets far too much airtime on this forum. Stepping out of an Iron man swim you wont be checking to see how many strokes you took. You will probably be looking to see what your heart rate is. But strangely, no one seems to train to heart rate for the swim.
My personal view is that the thing is of marginal, if any, benefit. I would add the squids to the coaching budget or to the budget for a better set of wheels. Or at least defer a decision on purchase till after the coaching.