I am searching for a type of sensor which will make arduino to make a sound , If I leave the car with door open and go far from the car.
I can handle open door sensor ,my question how can I make arduino which is inside the card , that I leaft the car and I am away with more than 5M for example ,
I think to use Bluetoth with my mobile in my hand and the car, Is there any other idea.
a second question
New model for the card can detect the key is it inside or outside the car itself, how can I do this ?, I need to prevent locking all door if the key is inside the car