This work is about the development of a prototype on a mobile device which is used for the test of a cars brake systems. Therefore, current researches in the field of mobile user interfaces are used. Since the application is practical it will be supported with findings though the analysis method of Contextual Inquiry about the user and the field of application. These findings will be analyzed and shaped into a design which uses live values from the examination equipment. This design will be used to build and evaluate gradually a low fidelity prototype and a high fidelity prototype.