I think they are great ideas. Not sure if there's much money to be made though. But it's great for the consumer cause it's cheap and there's no mess.
But I would be causious with taking my dog to one. Cause I doubt they wash them clean them between every dog wash, and that just makes it a great place for all pathogens to breed.
But if they were cleaned properly and the place looked clean then I would use them. We used to have one here in Penrith but not sure what happened to it, think it was next to Coreen ave vet clinic?