The best license plate readers are the ones that not only optically lift those alphanumeric symbols off of either license plate but also does:

1. identify your car stereo bluetooth ID

2. any bluetooth devices on your vehicle

3. has direct access to national registry of stolen plates

4. and a mobile modem in which to send alerts with.

5. HD webcam auto-zooming to the driver's side of the vehicle.

6. lift On-Star ID

Hey, what do I know? I'm just spitballing out there.