Within the interdisciplinary SiMS project (http://ce.et.tudelft.nl/SiMS), we are focusing on the development of novel implantable, microelectronic devices. We are working toward the specification and design of a new system-level architecture that will enable the structured and standardized generation of different microelectronic implants, spanning a wide range of biomedical applications. Thus, the architecture shall be generic in nature, while exhibiting crucial traits such as ultralow-power consumption, highly fault-tolerant operation and small form factor. Core system > components are a processor architecture and assorted C compiler, biosensors and bioactuators for interfacing to the living tissue, a wireless transceiver unit and a power source, each addressed by one or more of the SiMS partners. In this presentation, we will start by discussing interesting findings from an extensive implant survey. The goal is to pinpoint crucial technological and medical trends in the field, motivating SiMS. We will, then, present specification details of the (so-called) SiMS processor as well as novel profiling benchmarks and design-space exploration tools employed. We will also provide preliminary synthesis results of a SiMS-processor prototype and we will conclude our talk with the contributions of this work, its current limitations and the intriguing challenges it creates for the future.