Our crawl space had one of those cheap wifi sensors from Home Depot and it saved us from a slow leak behind the washing machine last year. It's wild how many people don't think about water until it's literally raining inside their walls. Seems like every house I've been in has some spot where water just creeps in unnoticed, whether it's a toilet seal or a window frame. Honestly wish builders would make inspections easier instead of hiding pipes behind drywall with no access panels.