Gyrid is a mobile device scanner using Bluetooth and WiFi wireless technologies.

When there is a Bluetooth adapter connected to the computer, it continuously
scans for Bluetooth-enabled devices which are publicly visible. Their
hardware id's are saved to a logfile including a timestamp and their device
 class (which is a code that indicates whether the device is a phone,
a carkit, etc.).

With a WiFi adapter attached, Gyrid monitors the radiospectrum for wireless
activity and logs received packet information. With respect to users privacy,
only the 802.11 packet headers are logged, not the packet contents.

The idea behind this is scientifical. When multiple of these scanners are placed
at known positions, the logfiles can be combined into a (geo)database and used
for further analysis. This can be done in realtime via a network server or in
postprocessing.