Abstract: The disclosure is generally directed to systems and methods for receiving from a mobile device that is optically tethered to a vehicle for remote driver assistance, an estimate of a speed of the vehicle, an orientation of the vehicle and a trajectory of the vehicle, comparing the estimate of the speed, orientation and trajectory received from the vehicle with a measured speed determined by one or more vehicle sensors, and preventing vehicle motion if a threshold difference from the comparison is exceeded. Another method is directed to determining at a mobile device an estimate of a speed of a vehicle, an orientation of the vehicle, a trajectory of the vehicle and a time stamp, transmitting the data to the vehicle, and untethering from optical tethering if the data are outside of a threshold or if the data indicate that the mobile device is tethered to an unintended vehicle.