The patents—"Automatic identification of vehicle location" and "Vehicle location in weak location signal scenarios"—describe how an iOS device could automatically detect when you've parked your car and then guide you back to it, even with crappy connectivity.
First, the phone could work out when the car is parked, by establishing some kind of data connection — Wi-Fi or Bluetooth, say — and then using a signal like the driver's door opening or the ignition system switching off (or a combination of them) to indicate that the car is parked. Then, the clever bit: the phone would track the user's motions independently, relative to the car.
A bit like a breadcrumb trail, the phone could use "on-board sensors to estimate with some accuracy the movement of a user". Presumably that would involve motion-data processing, time stamps, gyroscope data, pedometer data, and whatever other sensor is on board. Then, it would be able to flip the movements in order to guide the user back to their vehicle.
Sounds neat, right? But, as ever, it's worth noting that this is a patent. While it's a wonderful idea and it does suggest that Apple is taking its car-phone integration more seriously, it's by no means certain that such a feature will appear on iOS any time soon. Still, it doesn't hurt to dream. [AUSPTO(1) and VUSPTO(2) via Apple Insider]