So the interface to the computer is your first point. I see a future where wearable glasses, dockable phones: so you can use a big monitor when you're at home, some sort of projection, e-ink displays, are going to become much more usable.

Identity, either through a phone or some other mechanism. Phones can't really guarantee identity, they can take factors that are hard to duplicate, to indicate identity but they can't guarantee it. So fingerprint is a good example, the phone knows your fingerprint, you apply your finger to the fingerprint reader, and you validate to the phone you're probably the person registered.

Access Management, once you have established identity then you want to delegate access in your example for a few hours to a car, or some other mechanism. Given that most computers are network nowadays, if you're reasonably happy with the identity provided by a phone, access management of a car is trivial. We could probably set something up today that does what you want.

Heck Toro the Airbnb for cars does something like it already. Your phone unlocks the car and etc etc etc