Mobile phones allow for the use of all kinds of applications, and their mobile applications often provide similar functionalities as desktop applications. However, they are constrained by the limited screen size of the mobile device. Accordingly, designs of mobile user interfaces require optimization for small screens. As a consequence, users are provided with less context and often have to switch views or resize content such as maps or pictures. We present Mobies, a novel approach for extending mobile user interfaces by using external screens (e.g., the mobile phone and a large screen). Users can utilize more space and can thus overview a larger information context. We present a novel interaction and application concept and describe how user interfaces can be spanned across displays. Further, we contribute an original approach for using Near Field Communication to detect the devices’ spatial relation. We report on a user study which compared Mobies with standard mobile settings. Results from the system usability scale show that interaction with Mobies is subjectively more usable. Furthermore, it provides higher perceived information clarity and supports faster sharing of information to others.