Why not a voice menu? In addition to a physical interface. For most functions recognizing just a handful of words would do the job, like <wakeup word>, one, two, three .... You could shut off the air conditioner like

  you: "hello hal"
  hal: "say one for radio, two for air cond..."
  you: "two"
  hal: "say..."
  you: "three"

You wouldn't want a voice recognition app to steer or brake, but it would be reliable enough for changing the radio station or toggling overdrive. Are there high end cars that have voice control stock?