Good idea, but spotty customer service.
I used this company all last year successfully. But this year a host canceled my reservation. Swimply gave me the option to get a refund to my credit card, or to rebook in another pool with 10% off. I chose the second option, but they didn't make it possible, and then refused both! I had to agitate to get my money back, and even then they said no, but I checked my credit card and it had been refunded. I would say it's a great idea, good app overall, but they have rather poor customer service. If you don't need a refund, it's probably fine.