In a brush-less DC (BLDC) motor the commonly used speed is sensed using the feedback from Hall effect sensors and the back or counter EMF. The linked article on Wikipedia also mentions that 'Other sensorless controllers are capable of measuring winding saturation caused by the position of the magnets to infer the rotor position.'.
Are these the only possible sensors used to sense the speed? Additionally, how can we estimate the load torque in a practical and commercially available BLDC motor?