But even after eliminating the Uno from your selection ... mm in width and weighs about 13 g. The Nano, on the other hand, comes in the smallest form factor Arduino offers, with the same 18 ...

An Arduino Nano controls two relays which in turn can turn the car on, start it, and turn it off. Instead of adding a button for “push to start” he opted for a 13.56MHz RFID module.