Systems, methods, and devices for controlling and limiting use of functions, such as calling, texting, chatting, emailing, Internet surfing, and similar applications, on a mobile device when the mobile device is in a moving vehicle, includes use of an on-board computer installed within the vehicle, a transmitter in electronic communication with the on-board computer that periodically transmits speed data of the vehicle to a receiver installed on the mobile device, wherein the mobile device includes suitable software and a rules-based policy that define and control when and which functions of the mobile device are disabled or interrupted by the software when the vehicle is in motion above a minimum threshold speed. Policies are set by default but may be customized for particular individuals, devices, or circumstances. Policies may also be customized for particular groups or subgroups of employees or contractors for company or legal compliance to reduce distracted driving.