A portable device includes a safety feature that prevents some forms of use when the device is moving. The device may detect its speed or movement, compare that to a threshold, and provide a response or blocking function upon exceeding that threshold. The device may be a cell phone configured to disable transmission and reception of voice/text, conceal its display screen, and disable incorporated features and functions, if the cell phone is moving faster than walking speed or the movement is uncharacteristic of walking. The blocking function may be partially overridden based on a safety policy, which can be managed and customized. The introduction of hands-free devices may serve to override a blocking function and enable other functions.