What I want is my prius key as a front door key. Basically it can tell that you're within some very short distance, and opens. It can use strong cryptography i

What I want is my prius key as a front door key. Basically it can tell that you're within some very short distance, and opens. It can use strong cryptography instead of using a mechanical setup, and still have a physical "key" that denotes permission (allowing you to give & take permission to others).