It's like the Summon feature. "Will come to you across the parking lot with no intervention while you deal with a fussing child".

Must have vision of vehicle at all times. Must maintain one finger on dead man's switch on phone. Vehicle owner must not be distracted.

(Oh, and it may well drive through your half-opened garage door because there's no sensors at that height, and nothing could ever go wrong with a garage door, right?)