The first step to improving public health is by the assessment of vital signs, which are valuable indicators of overall health. In the present day there are a number of complex, albeit expensive instruments that can measure various parameters accurately. However, these instruments often tend to be bulky, expensive and difficult to operate. Hence it is difficult to use these instruments in isolated locations such as rural or disaster stricken areas, for bedside monitoring or even in military camps. The objective of this paper is to introduce the concept of a user friendly modular system which can be used to monitor various physiological parameters efficiently. In the proposed system different sensing circuits are attached to a common MicroController Unit (MCU) which can be updated with the associated firmware. Any general computing system such as a laptop is connected to the MCU via a USB-UART bridge. After the connection is established the controller starts sending data to the computer. A JavaScript is run on the laptop using open-source software called Processing 2.0, which initiates a customized display of the various parameters using the incoming data. For data logging we store the serial data in text files. As proof of principle we have measured two parameters, namely the body temperature using the LM35 sensor and the heart rate using photoplethysmography. Such a switchable system can be used as a tool to measure various parameters like oxygen saturation, blood pressure, ECG etc. on the computer screen.