You can use a handset with its SIM card on WiFi without a tower ever again if you provision the SIM card on its home network once. Nobody is suggesting using anything but a handset.

"Yes. There is a database they query to see if it’s tied to a handset, or just a virtual number."

Or they do an API lookup and query the type in realtime.

Elsewhere in this thread I posted the syntax for performing this lookup using the twilio API ...