Background: Stress-related disorders and chronic diseases are increasing globally, highlighting the need for integrative health indices that go beyond isolated physiological signals. Objective: We introduce the Physiological Wellness Index (PWI), a wearable-compatibl e composite that integrates autonomic, respiratory, and electrodermal domains into a single interpretable score for real-time wellness monitoring. Methods: The PWI synthesizes heart rate variability (HRV, proxied through PRV RMSSD), respiratory rate (RR, a s the operational proxy for Breathing Efficacy), and electrodermal activity (EDA) through a weighted normalization framework. Each signal is scaled per participant, with RR and EDA inverted so that higher component values consistently reflect better physiology. The index outputs a 0–100 score, mapped into three actionable categories: restful (70–100), active (40–69), and distressed (0–39). The validation was performed on the ZU-PWD ’25 dataset, comprising 28 adults, 15 months of monitoring, and over 900,000 minute-level records collected using Empatica Embrace Plus devices. Results: Despite heterogeneous data coverage, the PWI reliably distinguished baseline from stress days and tracked acute episodes characterized by EDA spikes, suppressed HRV, and elevated RR. The composite index classified data with greater stability and offered trajectories that were more easily interpreted compared to single-signal measures. Conclusions: The PWI represents a transparent, sensor -driven alternative to traditional fitness and wellbeing metrics. By addressing raw multimodal physiology with actionable states, it supports preventive healthcare, workplace and educational wellness, and clinical decision -making, marking a significant step forward on the IoMT landscape.