intelligent car park

I am trying to automate the entrance of a car park. intended to use a bluetooth device on the cars and at the entrance. the idea is that my system will use bluetooth communication to identify the owner of the vehicle and start billing them. the system will be subscription based (clents will have to register in advance before they can use the system)

1. which bluetooth device can be place on the vehicles for purposes of identification?

2. how do i interface this bluetooth device with my laptop(it does not have blue tooth)?

3. which is the best programming language to use?

4. can the bluetooth signal go through metal and where on the vehicle is most appropriate for implanting the device?

Unless this is a school assignment there is no way you should be stuck on #2.