Pediatricians could be focusing on recommending less television viewing, for instance, and more physical activity, as well as advising parents to limit children's consumption of juices and sugar-sweetened beverages.
This was the first instance since the New Deal in which the Court struck down a federal effort to regulate economic activity under the commerce clause.
Water can be easily stored and consumers have less discretion over when they use it (for instance, people cannot defer going to the toilet, which uses more water than any other activity at home), so the case for smart water meters is weaker.