Extending the Senses of Ubiquitous Devices

Modern smart devices are equipped with numerous sensors that can serve new functions beyond their original design when repurposed through side-channel sensing. Side-channel sensing involves leveraging existing sensors in unconventional ways to detect subtle signals and gather information beyond their original intended purpose. This work explores the untapped potential of side-channel sensing to enhance the functionality of existing smart devices, particularly in addressing niche user needs. I present two approaches: The first technique involves low-cost, low-power sensor add-ons that users can attach to their devices, enhancing functionality without any internal modifications to the device. I showcase GlucoScreen, a smartphone add-on that leverages the capacitive touchscreen for blood glucose monitoring, and WatchLink, which allows users to connect external sensors to their smartwatches via the ECG interface. The second technique focuses on manufacturers making targeted upgrades to existing hardware to improve functionalities at reduced time and cost. I present Z-Ring, a ring wearable that expands the bandwidth of bio-impedance sensing to enable micro-gesture interactions and object identification. Our findings highlight the potential of side-channel sensing to create more personalized and adaptable technology.