An embodiment of a portable sensor input device operatively connects to a smartphone, wearable computer device, tablet PC, and/or other mobile computer device to facilitate medical examination and diagnosis. The sensor input device used for biological signal detection contains one or more sensors inside its chest-piece, such as, without limitation, acoustic sensor, temperature sensor, pressure sensor, light sensor, image sensor, electrocardiogram (ECG) sensor, and/or ultrasonic sensor. The ergonomically designed and shaped input device can employ an energy harvesting module to power up the sensor system. A medical application software inside the mobile computer device controls the sensor input device and performs the major functions.