Très cool.
My rental has no key. Or rather, it has this little plastic brick for a key:
La Clé
About the size of a credit card and just under a quarter-inch thick
(The 0.50€ coin is about the size of a US quarter.)
The little buttons on the key let you open the doors. Once inside the car, the whole key slides into a slot in the dashboard. After you’ve inserted the key, the ignition is nothing more than a “start” button.
Très cool, if a little clunky to carry around.