Embodiments are directed to a trailer maneuvering assistant system onboard a vehicle to communicate with and receive control instructions from a mobile device app. In one example embodiment, the app interface presents the user with an engagement input area and a curvature command area. The user must provide two types of touch inputs to the user interface portions: a first touch input that includes a complex gesture input in the engagement interface portion. In one example embodiment the complex gesture may be user input of a closed geometric shape such as a circle, oval, rectangle, or some other shape. The input may be complex in that it matches a canonical model for the respective shape. Matching may include an input that is coterminous with the canonical model within a threshold amount of error, and/or meets another guideline or threshold such as being a closed shape, or some other predetermined requirement(s).