Low-power microcontrollers lack some of the hardware features and memory resources that enable multiprogrammable systems. Accordingly, microcontroller-based operating systems have not provided important features like fault isolation, dynamic memory allocation, and flexible concurrency. However, an emerging class of embedded applications are software platforms, rather than single purpose devices, and need these multiprogramming features. Tock, a new operating system for low-power platforms, takes advantage of limited hardwareprotection mechanisms as well as the type-safety features of the Rust programming language to provide a multiprogramming environment for microcontrollers. Tock isolates software faults, provides memory protection, and efficiently manages memory for dynamic application workloads written in any language. It achieves this while retaining the dependability requirements of long-running applications.

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Fine-grained energy metering in homes and buildings provides a promising technique for addressing the unmaintainable energy consumption levels of worldwide buildings. Metering electricity, lighting, natural gas, HVAC, occupancy, and water on a per appliance or room basis can provide invaluable insight when trying to reduce a building's energy footprint. A myriad of sensor designs and systems collect data on particular building aspects, but are often hampered by installation difficulty or ongoing maintenance needs (like battery replacement). We address these common pitfalls for water and heat metering by developing a small, energy-harvesting sensor that meters using the same thermoelectric generator with which it powers itself. In short, the rate at which the harvester captures energy is proportional to the heat production of the monitored appliance or pipe and this relationship allows us to estimate energy use simply based on the sensor's ability to harvest. We prototype our sensor in a bracelet shaped form-factor that can attach to a shower head pipe, faucet, or appliance to provide local hot water or heat metering.

City-scale sensing holds the promise of enabling deeper insight into how our urban environments function. Applications such as observing air quality and measuring sources of noise pollution can have powerful impacts, allowing city planners and citizen scientists alike to understand and improve their world. However, the path from conceiving applications to implementing them is fraught with many challenges. A successful city-scale deployment requires physical installation, power management, and communications-all challenging tasks standing between a good idea and a realized one, suggesting the need for a platform that enables easy deployment and experimentation of city-scale sensing applications. To address these basic challenges, we present Signpost, a modular platform for city-scale sensing. Signpost simplifies deployment and installation in cities by removing the need for connection to wired infrastructure and instead harvesting energy from an integrated solar panel.The platform provides the key resources necessary for its pluggable sensor modules to support city-scale applications. Signpost stores excess energy for later use, distributes energy between modules, and provides communication through multiple wireless protocols. It also offers local storage for sensor data and allows for additional processing in a duty-cycled Linux environment.

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