damdam writes "A Dutch guy seems to have set up a small network of bluetooth scanners. He has all the information logged to a central database and you can search it over the web. On his website it says "Some of these matches were only minutes apart. Therefore I could even calculate the approximate speed of someone moving from one location to another.". There are also some interesting statistics on his site showing traffic volume in his hometown (based on bluetooth signals) and he even lists popularity of certain Nokia phones. It's interesting to see how much information an individual can gather using old equipment."