Development of a Mobile Application for Remote Vital Signs Monitoring Using Smartphone Sensors in Delta State

Smartphone-based health monitoring offers a low-cost pathway for extending vital sign tracking to patients in resource-limited communities in Delta State, where access to dedicated monitoring devices is restricted. This study develops a mobile application for remote vital signs monitoring using built-in and Bluetooth-connected smartphone sensors, targeting heart rate, respiratory rate, and skin temperature measurement. The Android application was developed in Java using Android Studio, integrating the smartphone rear camera flashlight for photoplethysmography-based heart rate measurement, the built-in accelerometer for respiratory rate estimation via chest expansion motion, and a Bluetooth-paired DS18B20 temperature sensor module for skin temperature. Signal processing algorithms implemented within the application include peak detection for PPG heart rate calculation, spectral analysis of accelerometer-derived respiratory signal, and digital low-pass filtering for temperature data. The application transmits readings via a Wi-Fi or mobile data connection to a cloud-based dashboard accessible by a supervising clinician. Validation testing was conducted on fifty volunteers at a community clinic in Warri, comparing app-derived measurements against clinical reference instruments. Heart rate showed a mean absolute error of 2.9 beats per minute, respiratory rate showed a mean absolute error of 1.8 breaths per minute, and skin temperature showed a mean absolute error of 0.4 degrees Celsius. Battery drain testing confirmed acceptable energy consumption per thirty-minute monitoring session. The study recommends expanded validation on patients with cardiovascular and respiratory conditions, and integration of an alert mechanism for out-of-range readings. Keywords: mobile health, vital signs monitoring, smartphone sensors, photoplethysmography, Delta State.