It's already out.
You can download this app ahead of time https://nowserving.seriousmd.com/
You cannot use the Now Serving app until you get a link from the doctor.
Once your doctor sends you a message with your unique link, just tap it and you'll be able to get into the app to receive your doctor's call.
This is just one of the security measures we have in place to make your patient-doctor consultation private.