HHS Issues Guidance on Audio-Only Telemedicine Services: The guidance is pretty straight-forward and common-sensical: audio-only telehealth is fine from a HIPAA standpoint as long as reasonable steps are taken to protect privacy: no speakerphones except in private spaces, and verify the identity of the patient.
Of course, doctors have been talking to patients over the phone for some time . . .
AND, just because it's OK under HIPAA, that doesn't mean it qualifies for payment under Medicare, Medicaid, or private insurance; check your provider agreement before billing.