There's the button that unlocks the car's doors and the one that pops the trunk. And then, on some BMWs, the key fob has a button with a diamond on it.

Knizek says the iPhone setup process for BMW’s digital key can be time consuming, but when complete, it was fairly easy to get into and start up CR’s rented BMW M440i xDrive with the iPhone.

BMW says it will last for up to 3-months on a charge. A display key fob with display was already available as a one off for the i8 Concours d'Elegace Edition 2014.

A high-tech key fob with a digital screen sounds and is pretty neat, but the BMW 7-Series' new Display Key has an even neater feature, as it allows you to ...