We investigate if it is possible to reconstruct a mobile phone’s mobility using its Bluetooth contacts with other mobile devices, some of which are equipped with GPS receivers. Our data mining analysis, based on two different data sets, shows that in certain environments coarse grained mobility of a significant portion of mobile phones can be obtained using this technique. For this reason, anyone capable of collecting Bluetooth and, if available, GPS logs for a large population of mobile phones, represents a serious privacy threat for all users with discoverable Bluetooth devices in the area.