We explore the high potential of elastic controllers for casual interaction in mobile and ubiquitous computing scenarios. While several remote interaction techniques with handheld or body-worn devices have been proposed, the usage of string-based, elastic interaction is still underexplored. Therefore, we first introduce a systematic design space along the axes reference system, interaction dimensions, sensing methods and haptic feedback. Our main contribution is Elasticcon, a versatile, wearable device with a retractable string and a set of exchangeable traction knobs. This elastic controller provides several degrees of freedom and allows rich interaction techniques. As a result of an iterative design process, we also contribute two working prototypes for belt-worn and handheld use. To demonstrate their versatility, we implemented several promising application scenarios. We tested Elasticcon in three smaller user studies investigating qualitative usability aspects and found initial evidence for elastic controllers as being comfortable, casual and yet accurate interaction devices.