BSM or Blind Spot Monitor is on many cars this days including the Toyota Camry Atara SL and Hybrid Luxury and the Aurion Presara and Sportivo ZR6. Seeing as you cannot always see what is coming, The BSM acts as a 2nd pair of eyes.
The system uses sub-millimetre radars around the car to monitor the cars blind spots, so for example if you indicate to change lanes and there is something in one of the car’s blind spots, a light will show up on the respective door mirror.
The Monitor is automatically activated at speeds of around 40 km/h and above, the system is smart enough to detect anything larger then a 125cc motorcycle, and also smart enough to ignore stationary vehicles, vehicles that are more then one lane away or are heading the other direction.
Of course BSM is only a guidance device so it should not be completely relied on, the area that the vehicle is being driven in should be monitored by the driver.