Specifically, the intent is to use a separate microcontrollor board (Arduino, RPi, etc.) between the Cortex and a set of custom sensors.
The main purpose of this additional microcontroller board would be to interface with sensors that would otherwise not be available to use with the Cortex. In addition, the microcontroller board would filter and perform computations on the sensor data that would otherwise be impossible or extremely difficult to implement on the Cortex (such as Kalman filters, particle filters, or a SLAM process).
The microcontroller board would only perform calculation on the sensor data and output the results to the Cortex. If it were removed or disconnected, the robot would continue to function and drive, although in an impaired manner. The significance of this is that the Cortex remains the “master” controller and is not simply a motor driving slave to the additional microcontroller board.