We developed a health monitoring system based on the smartphone. A compact and low-power-consuming biosignal monitoring unit (BMU) measured electrocardiogram (ECG), photoplethysmogram (PPG), temperature, oxygen saturation, energy expenditure, and location information. The 2.4 GHz Bluetooth(®) (Bluetooth SIG) network in the BMU communicated with a smartphone. Health information was sent to a remote healthcare server through a built-in 3G or Wi-Fi network in the smartphone. The remote server monitored multiple users in real-time. Normally data of vital signs were being transmitted to the server. In an emergency or for a special care case, additional information such as the waveform of the ECG and PPG were displayed at the server. For increased transmission efficiency, data compression and a simple error correction algorithm were implemented. Using a widespread smartphone, an efficient personal health monitoring system was developed and tested successfully for multiple users.