Synthetic biology aims to create functional devices, systems, and organisms with novel and useful functions taking advantage of engineering principles applied to biology. Starting from the first demonstration of synthetic circuits in bacteria more than a decade ago, synthetic biology has substantially advanced strategies for biomedical applications. Ultimately, sophisticated therapeutic sensor-effector devices that connect diagnostic input with therapeutic output may provide platforms for future gene- and cell-based therapies. However, synthetic--biology-based devices are still far from becoming clinical reality, especially due to the complexity of cellular and environmental systems to be encountered. Cell-free systems offer a unique platform for expanding the capabilities of synthetic biology by reducing complexity, removing structural barriers, bypassing requirements of viability. Building on the richness of DNA computing, strand displacement circuitry, and transcriptional circuitry, we show how cell-free systems using a small set of biochemical components can exhibit a wide range of functional behaviors --- a step towards autonomous behaviors and biomedical applications.