Indeed, you're right. It follows a similar model to services that do appointment reminders via text message, which is becoming very common.

The permission check becomes vital: it's part of the patient authorization at, for example, a first visit, and is best when also followed by a verbal authorization upon checkout. It's one of the big hurdles we're trying to overcome obviously, but we believe there are proper ways to do it and make it work within the boundaries of regulation and privacy. No good problem worth solving is without difficulties, right? :)