[m463]

I thought apple already had ML functions like this for facial unlock.

They also used to provide transcripts of voicemail done locally on the phone (although it was not great accuracy)

[gen3]

They also use ML for "Hey Siri" and the face detection in the photos app.

Edit: Here is the article where apple talks about how "Hey Siri" works: https://machinelearning.apple.com/2017/10/01/hey-siri.html