I don't see this as a Walmart play. Part of the problem is that the retail price is $700. There aren't many people that would spend that, IMO (and I don't think Walmart would have any part of it). Water quality in the US is, overall, very good. Problems that crop up (Flint, natural disasters) are rare and unpredictable so few would purchase a $700 device "just in case." Need to ramp up sales volume (most likely to commercial/govt/military buyers), and reduce production costs. Then you can get retail price down to $299, where it would be a more manageable purchase. At that point I'd see it being a Cannibis play, because if I'm going to drop $200/month on weed I'd like to be able to verify what I'm buying. I still think water and air testing is for govt/military/acutely sensitive individuals.
I don't have a need for one (Canna, water, or air). But I hope a lot of other people do. In fact, I'm betting on it : )
