The BluFax Concept
What is Bluetooth?
Bluetooth is a telecommunications industry specification that defines the manner in which mobile phones, computers, personal digital assistants, car radios, and other digital devices can be interconnected using short-range wireless communications. Bluetooth uses a low cost transceiver chip to to exchanges information with other Bluetooth devices within a globally available frequency band of 2.45 GHz.
Device IDs. Every Bluetooth devices has a unique 48-bit address, that is extremely difficult to track back to an individual user. A full device ID may look like this: OO:18:AF:4B:56:BD. The first half of the number (00:18:AF) is assigned by the manufacturer. The second half of the nuber (4B:56:BD) is associated with that device. This information is not stored in accessible databases. While device IDs are unique, BluFax units collect no personal information as part of this process [More information on Privacy Issues]. .
Detectable Signals. Bluetooth transceivers that are powered on and are set in the "discover" mode continuously transmit their 48 bit ID (address) for the purpose of identifying a device to communicate with; and to establish a link with the “responding devices”. This process is continuous, and willl transmit inquires even if, for example, someone is talking on a mobile phone using a head set.
Traffic Data Applications
The ability to identify and record unique IDs for devices that pass sensor units. Each BluFax contains GPS and syncronize with a common time reference. 
Travel times and space mean speed are calculated by BluStat software by searching for common IDs recorded by pairs of stations and comparing the time and location.