GEYIREN A900 Car HUD OBD RPM Meter Head-Up Display Overspeed Warning System Car Accessories Water Temperature Alarm *Q: What is HUD (Head-Up Display)? HUD (Head-Up Display) can project the driving info on the front windshield, and keep the driver’s eyes always on the road when driving,for safer driving. OBD2 HUD: Connects to the car by OBD cable, suitable for most of cars after 2003 years in USA/Europe/Australia, and after 2007 years in Asia. HUD Products don’t support JOBD and OBDI. GPS HUD: Connects to the car by the cigarette lighter, suitable for all cars and trucks.