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.