Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for wireless user interface projection for vehicles are disclosed. In one aspect, a method includes the actions of receiving, by a mobile device, a wireless signal transmitted by a processing unit of a vehicle that includes a screen, the wireless signal including an identifier for the processing unit. The actions further include determining that the identifier corresponds to a trusted processing unit to which the mobile device is configured to provide projected UI information. The actions further include automatically establishing a wireless connection between the mobile device and the processing unit that is associated with the identifier. The actions further include automatically providing, by the mobile device, projected UI information to the processing unit for display on the screen of the vehicle.