A 405nW/4.8μW four-mode sensor interface IC with reconfigurable voltage/current/ resistive/capacitive channels for various healthcare use cases is presented. We demonstrate an example use case for multi-modal physiological and environmental co-sensing with 1) a 3nW ECG V-channel, 2) a 13nW respiration rate C-channel, 3) a 2.3μW PPG I-channel, 4) a 57nW ozone R-channel, 5) and 35.9-79μW red/infrared/UV LEDs. The ozone channel proposes a sensor saturation detector for intelligently controlling UV LED, resulting in 5x LED power improvement. A context-aware event-driven architecture is implemented to flexibly dial the system power from full-measurement mode 83.8μW down to a floor of 405nW.