I'm planning on making a keyless entry and pushbutton start for my classic car. I have found an active rfid fob from china that was arduino compatible, but it doesn't sound like it has any security features built into it. I want to explore some other solutions that will help me achieve my goals:
Secure: possibly writing a rolling code feature
No user interface: I want the doors to unlock when i approach the vehicle. as long as it's getting a signal it will allow me to start the car. if the fob is out of range then it locks the doors and deactivates the starter mechanism.
Low Power, I'd like for this to not drain my car battery on the vehicle side of things and i'd like for it to last months on a coin cell battery.
Some options I have been considering: limit the range of one of these by adjusting the size of the antenna: http://www.kickstarter.com/projects/flutterwireless/flutter-20-wireless-arduino-with-half-mile-1km-ran?ref=search
but i'm not sure that either one of these will be a good option. can anyone give me some advice, or a direction to look to for a possible solution to my project?