HEALTHCARE in the 21st century is changing rapidly. In advanced countries, in particular, healthcare is moving from a public to a more personalized nature. However, the costs of healthcare worldwide are increasing every year. Better use of technology can and should be used to get control of these costs. At the same time, implants have clearly benefitted from the astounding technology-miniaturization trends of late, boasting smaller sizes, lower power consumption and increased performance of the transistor devices. However, such advances do not come for free. Adverse effects in current implant designs are being witnessed, such as increasing power consumption, absence of design for reliability and highly application-specific nature. Operating under the assumption that implants will constitute an important means towards improved, personal healthcare and, in view of the aforementioned design phenomena, we believe that a new paradigm in implant design is required. This dissertation establishes the concept of Smart implantable Medical Systems (SiMS). SiMS is a systematic approach – a framework – for providing biomedical researchers and, hopefully, industry with a toolbox of ready-to-use, highly reliable implant sub-systems and models in order to construct optimal implants for various medical applications. The SiMS framework has to guarantee essential attributes, such as high dependability, modular design, ultra-low power consumption and miniature size. Having defined the SiMS framework, this dissertation is, then, concerned with exploring the optimal microarchitectural details of a crucial SiMS component: the SiMS processor. Contrary to the current state of the art, this processor aspires to be a new universal, low-power and low-cost processor and capable of efficiently serving a wide range of diverse implant applications.