{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,28]],"date-time":"2025-10-28T10:07:26Z","timestamp":1761646046776,"version":"build-2065373602"},"reference-count":17,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2016,3,11]],"date-time":"2016-03-11T00:00:00Z","timestamp":1457654400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In our preliminary study, we proposed a smartphone-integrated, unobtrusive electrocardiogram (ECG) monitoring system, Sinabro, which monitors a user\u2019s ECG opportunistically during daily smartphone use without explicit user intervention. The proposed system also monitors ECG-derived features, such as heart rate (HR) and heart rate variability (HRV), to support the pervasive healthcare apps for smartphones based on the user\u2019s high-level contexts, such as stress and affective state levels. In this study, we have extended the Sinabro system by: (1) upgrading the sensor device; (2) improving the feature extraction process; and (3) evaluating extensions of the system. We evaluated these extensions with a good set of algorithm parameters that were suggested based on empirical analyses. The results showed that the system could capture ECG reliably and extract highly accurate ECG-derived features with a reasonable rate of data drop during the user\u2019s daily smartphone use.<\/jats:p>","DOI":"10.3390\/s16030361","type":"journal-article","created":{"date-parts":[[2016,3,14]],"date-time":"2016-03-14T11:03:45Z","timestamp":1457953425000},"page":"361","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Sinabro: A Smartphone-Integrated Opportunistic Electrocardiogram Monitoring System"],"prefix":"10.3390","volume":"16","author":[{"given":"Sungjun","family":"Kwon","sequence":"first","affiliation":[{"name":"Interdisciplinary Program in Bioengineering, Graduate School, Seoul National University, Seoul 08826, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dongseok","family":"Lee","sequence":"additional","affiliation":[{"name":"Interdisciplinary Program in Bioengineering, Graduate School, Seoul National University, Seoul 08826, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jeehoon","family":"Kim","sequence":"additional","affiliation":[{"name":"Interdisciplinary Program in Bioengineering, Graduate School, Seoul National University, Seoul 08826, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Youngki","family":"Lee","sequence":"additional","affiliation":[{"name":"School of Information Systems, Singapore Management University, Singapore 178902, Singapore"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Seungwoo","family":"Kang","sequence":"additional","affiliation":[{"name":"School of Computer Science and Engineering, KOREATECH, Cheonan, 31253, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sangwon","family":"Seo","sequence":"additional","affiliation":[{"name":"The 7th R&amp;D Institute, Agency for Defense Development, Daejeon, 32024, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kwangsuk","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, College of Medicine, Seoul National University, Seoul 03080, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,3,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Task Force of the European Society of Cardiology (1996). 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Proceedings of the 9th ACM Conference on Embedded Networked Sensor Systems, Seattle, WA, USA.","DOI":"10.1145\/2070942.2070970"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Riener, A., Ferscha, A., and Aly, M. (2009, January 21\u201322). Heart on the road: HRV analysis for monitoring a driver\u2019s affective state. Proceedings of the 1st International Conference on Automotive User Interfaces and Interactive Vehicular Applications, Essen, Germany.","DOI":"10.1145\/1620509.1620529"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Salahuddin, L., Cho, J., Jeong, M.G., and Kim, D. (2007, January 22\u201326). Ultra short term analysis of heart rate variability for monitoring mental stress in mobile settings. Proceedings of the Engineering in Medicine and Biology Society, 29th Annual International Conference of the IEEE, Lyon, France.","DOI":"10.1109\/IEMBS.2007.4353378"},{"key":"ref_6","unstructured":"Polar Heart Rate Sensor. 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