A device that can help prevent drivers from falling asleep while driving is often referred to as a "Driver Alert System" or "Driver Fatigue Warning System." These systems use various technologies to monitor driver behavior and alert them if they show signs of drowsiness. Some common types include:

1. **Lane Departure Warning Systems (LDWS):** These systems use cameras to detect lane markings on the road. If the vehicle starts to drift out of its lane without signaling, the system will issue an audible warning, vibration in the steering wheel, or a seat vibration to alert the driver.

2. **Forward Collision Warning Systems:** While primarily designed to prevent rear-end collisions, these systems can also alert the driver if they become too drowsy and fail to react to traffic ahead.

3. **Eye Movement Monitoring Systems:** Some advanced systems use infrared cameras to track the driver's eye movements. If the system detects that the driver's eyes are closed for longer than a certain period or if the frequency of blinking indicates drowsiness, it will issue a warning.

4. **Steering Wheel Sensors:** These sensors can detect erratic steering movements which may indicate that the driver is becoming drowsy. The system can then provide an alert to the driver.

5. **Seatbelt Tensioners:** Some high-end vehicles have seatbelt tensioners that can tighten the seatbelt if the system detects drowsiness, serving as a physical reminder to the driver to stay alert.

6. **Fatigue Detection Systems:** These systems analyze various parameters such as steering wheel movement, vehicle speed, and time spent driving to determine if the driver is showing signs of fatigue.

These systems can significantly enhance road safety by helping to prevent accidents caused by driver drowsiness.