A large challenge was balancing the roles of the smartphone app and the onboard display. My initial idea was to focus upon the onboard display, but after much trial and error I discovered that a smartphone would indeed be needed as it was too unwieldily to enter lots of data. Therefore the roles of each device changed - the smartphone app became the main source of input, for fulfilling tasks such as creating users, entering data, unlocking the car and other functions which required precision, while the onboard display was used passive display and for simple tasks, such as lowering the windows or changing the volume. Instead of being an all-in-one package, the inbuilt display would be an extension of the smartphone app, built to be seen and used while in the car and powered by the smart phone app.
By creating a screen for each function, with the device itself being a button, resulted in a simple but powerful interface. The user is able to focus upon the action they are taking, and not lose themselves in menus, screens or other options. The entire screen becomes the button, controlled using simple gestures.