Several years back I had the same question and carefully researched an alternative. I had got Duxback a few times but was finding it too expensive to justify as it is overpriced for what it is. Duxback is good though, lasts longer than products you apply yourself and seems to be more effective initially.
The good ones, from 30-40mph upwards will negate the need for wiper blades in rain conditions. The water just beads and flies off with the airflow.What do these products do that the wipers don't? (not being an 4rse, just genuinely don't know!)