The authors outline one path towards constructing interactive artworks with the potential for displaying novel behavior. They use Peter Cariani's taxonomy of adaptive robotic systems as a framework for comparing the capabilities of systems that interact with their environments. The authors then describe two examples of structurally autonomous systems that are able to construct their own sensors independently of a human designer. The first device, the evolved radio, is the result of a recent hardware evolution (HE) experiment conducted by the authors. The second device, the electrochemical ear, was constructed almost 50 years ago by the British cybernetician Gordon Pask. The emergent behavior in both systems is only possible because many conventional engineering constraints were relaxed during their construction. Using existing technology, artists have the opportunity to explore the potential of structurally autonomous systems as interactive artworks.