Yup. You also won’t be able to easily book Lightning Lane entrances without at least one person in your party having a smartphone.But a lot of people do, and they also have phones, which manage notifications very well even without a watch. I can't imagine the simple lights and vibration would be any use at all as a notification system just to tell you to then take out your phone to get the info.
This would be more useful if Disney wasn’t already starting to treat smartphone-free guests as second-class citizens.