If the car and phone are paired via Bluetooth, the doors unlock. Walk out of range and the car automatically locks when the connection drops. His build uses an Arduino Mega with a BlueSMiRF ...

Popular boards like the Arduino Uno, Nano, Micro, and Mega are great examples of this ... features different functionalities ...

Inside the radio there is an Arduino Mega controlling the breakout boards ... but we have had more than one bluetooth upgrade or addition of a line-in port. Thanks [Darkspr1te] for the story.