A device, method, and system for secure mobile data storage includes a mobile data storage device having a short-range communication circuit, a long-range communication circuit, and a data storage for storing data. The mobile data storage device is used to store data used by a paired mobile communication device. The mobile data storage device and the mobile communication device communicate control signals over a wireless control link established using the short-range communication circuit and data over a wireless data link, different from the wireless control link, established using the long-range communication circuit. The mobile data storage device and/or mobile communication device may monitor a distance between the devices and perform a security function in response the devices being separated from each other. The mobile data storage device may backup data on a remote data server and/or repopulate data from the remote data server using the mobile communication device.