Bluetooth Data Acquisition Project HELP!

Hi, I have this situation. I have to design a hardware that senses other bluetooth devices and stores the MAC ID's of the detected devices along with the time of detection. This device eventually will be installed on roads to acquire data about the number vehicles travelling. Now from where should i start this project?

A Bluetooth dongle will be used to sense the devices and from there on please tell me how to move about in this project. Just the idea will be enough for me to take over.

Thanks in advance. Cheers.