AbstractSilent hypoxia is a complication that can lead to severe respiratory disorders at a time when people feel well, especially in Covid-19, and lung destruction if not intervened early. In this paper, a wearable device and a mobile application synchronized with the device were developed to measure people’s vitals and reduce the risk of silent hypoxia. The device consists of 2 parts: a wristband and a finger-clip, and includes a micro-controller, a bluetooth module, a Li-Po battery and various sensors to measure body temperature, pulse and SpO2 values. It can measure body temperature, pulse and SpO2 instantly or at certain programmable intervals like a holter device through the mobile app. These measured values can be recorded and various analyzes can be performed on them. Also the measurement results can be sent via an e-mail. When the vitals reach or exceed the predefined risk levels, a notification can be generated. The proposed device was evaluated in various performance tests and compared to a commercial pulse oximeter as well as alternatives in the literature. It was tested for connectivity and transmission, battery endurance and field testing. In the comparison test, error values of 1.8%, 3.5% and 0.6% were achieved in SpO2, pulse and temperature measurements, respectively. The device is both a measurement and holter instrument for body temperature, pulse and SpO2 values. With this feature, it can be actively used by both patients and their relatives in hospital or home environment.