It doesn't have to be phone-based. It can just use park ticket/pass barcodes like the old Disney FastPass system. Scan your admission media at a little kiosk at the entrance to the ride, it tells you when to come back, and then you have to scan that same admission media to enter virtual queue entrance when your time comes up.
This is probably all outside the realm of this thread though. There are likely rich discussions to be had about both improving the queuing experience for standby guests and, separately, for aspirational approaches for replacing in-person, traditional queuing in parks entirely.