While I would love to have sentry mode, I think we're all missing the point. This is a safety issue and we need to be asking why our cars can't do sentry mode.
Think of it this way: If our cars can't reliably detect a pedestrian walking up to it or around it, why should we believe it can reliably detect a pedestrian standing still as we're moving slowly through a parking lot? Everything is relative to the observer so there isn't much difference between the two scenarios.
And if we can't trust our cars to detect pedestrians at low speeds, why should we believe it will detect a kid running out in front of us chasing a ball? Even at 25mph, the fraction of a second that the computer brakes before you react could be the difference between just wetting your pants and having to bury someone's child.
I want answers. Not because I want a cool feature; But because I need to know if standard safety features like blindspot detection and auto emergency braking will work if I'm ever unfortunate enough need them.
I have no doubt that it can detect cars. Hell, it's so good at detecting cars that it occasionally finds ones I can't even see! But when it comes to pedestrians, it's very rare that I see the person avatar show on my dash. Even when people are walking in front of my car at a red light, it's 50/50 if I'll see one or two of them detected. This concerns me and I think we all need to be asking different questions.