## 1 Introduction
Data are obtained from several wearable sensors, fused, and transmitted to a server as decision support system (DSS). The smart T-shirt integrates 3-lead ECG, a microphone as context-audio sensor, a pulse oximeter, two respiration bands (thoracic and abdominal), an accelerometer, and sensors to measure humidity, body and ambient temperature. Additionally, external sensors capture body weight, blood pressure, respiratory volume, and glucose level [49]. The \"WELCOME\" platform is proposed by [PERSON] et al. as a bi-directional approach between the COPD patient and a care center. The platform is composed of three modules named patient hub, cloud, and application. The platform measures parameters in the domains of heart failure, diabetes, anxiety, and lifestyle issues. The patient hub interacts with the patient via a light vest-jacket including in total 26 non-invasive sensors for: SpO\({}_{2}\), electrical impedance tomography (EIT), chest sound, multi-lead ECG, and activity tracking. The cloud implements storage server, feature extraction, and DSS [50]. In summary, comprehensive and efficient monitoring of COPD patients requires simultaneous assessment of all three domains of influencing factors: environmental, physiological, and behavioral parameters (Table 2). However, the state-of-the-art is focused on physiological and behavioral monitoring, or on designing platforms to combine separated devices, which all come with their individual overhead, synchronization, calibration, power supply and data transmission (distributed approach). However, chronic diseases in general and COPD in particular need convenient and integrated measures of environmental parameters such as hazardous and/or toxic gases (e.g., NO\({}_{2}\), CO, O\({}_{3}\)) and other pollutants, as they cause breathing and heart problems; UV radiation exposure, as COPD patients have an increased risk of skin cancer; and ambient sound level, as this impacts sleep quality and causes sleep disorders. Furthermore, conditions and priorities of COPD patients demand centralized data collection and processing with ubiquitous devices. Our previous work was concentrated on the design of wrist-worn hardware for monitoring environmental parameters. Hardware design, sensor calibration and fusion, power consumption, and data logging in internal memory while BLE disconnections have been discussed in Reference [51]. In this paper, we aim to design and implement a low-cost and convenient prototype for simultaneously monitoring of environmental, behavioral, and physiological parameters. As a focus of this work and an important aspect of wearables, we prolong the monitoring through a careful and seamless hardware design and software development. The work concentrates on technical development and its features rather than its clinical application to improve the flexibility and applicability of the prototype by enhancing the configurability and improving the wearability via downsizing the design. Therefore, we:  
* extend environmental and behavioral to physiological monitoring of skin temperature and heart rate,
* re-design the hardware to downsize the prototype and significantly improve its wearability,
* add a sensor layer that sticks at the bottom of the prototype directly touching the user's wrist,
* improve the signal quality of gas sensors by additional voltage reference,
* remove the sound pressure level module, design, and integrate the respective electronics circuit,
* eliminate mismatching impedance via a gain unity buffer, and
* add a UV sensor to complete the requirements for COPD patients and safety workplaces monitoring. To the best of our knowledge, we are the first to contribute a wrist-worn prototype that integrates all three (environmental, physiological, and behavioral) domains of health monitoring for COPD patients and industrial workers. Therefore, our concept and prototypical realization of an all-in-one and wrist-worn device may significantly contribute to personalized healthcare monitoring.