I wanted to do something like this a couple months ago but on a larger (although anonymous) scale, but haven't gotten around to it.<p>I live pretty much right at the corner of the 10 and 110 freeways in downtown Los Angeles, two of the busiest freeways in southern California, if not the country/world. The idea was to set up a high gain antenna pointing at the freeway, and track all the thousands, if not millions, of Bluetooth enabled cell phones that pass by every day.<p>Maybe I'm just a sucker for random statistics, but you could get some interesting data, like the relative numbers of phones from different manufacturers (I believe Bluetooth MAC address ranges are tied to manufacturers), traffic stats like the number of cars per minute, or even the speed of the cars determined by the period that a device stays within range.