All the electronic gadgets (like those mentioned here) and driver aids you find in cars these days are largely attributed to the emergence of high-performance computers. The real stars in cars, however, are those tiny devices we call sensors, because these things have evolved to become smaller, smarter and immensely more robust.
What this means is that sensors can be installed in tight spaces where conditions may be harsh (hot, high-vibration, extreme pressure), and yet supply the computer with accurate and timely data. Despite having grown smaller, the sensor’s role in the electronic management of the modern vehicle’s performance has never been so big. Every car manufactured today needs sensors in the engine (such as Honda’s DOHC VTEC wonders) and everywhere else to perform a bewildering array of functions.
To perform its function, a sensor must firstly be able to detect a change in its assigned parameter (e.g. temperature, pressure, body roll, etc). Each sensor is unique, being designed for a specific function. So a temperature sensor cannot be used as a pressure sensor, or vice-versa. In addition, a variety of scientific principles (magnetism, photo-electricity, piezo-electricity, etc) form the basis of a sensing device’s functionality.
Regardless of their form or function, all these sensors have one thing in common: the nature of their feedback signal. Whatever a sensor detects/senses (pressure, temperature, airflow, vibration), it converts the measurement into an electrical form (usually a voltage of between 0 and 5 volts) to send into the ECU (electronic control unit) where the analogue voltage is converted into a digital input. The current generation of ECUs rely on a combination of information from a multitude of sensors to control one parameter.
Microprocessors are now powerful enough to both send and receive a multitude of signals simultaneously, so it is just as well that micro-engineering has produced miniaturised sensors that tell the tale with consistency and accuracy. This is an important factor, because the ECU’s precision in ultimately controlling an actuator is limited by the accuracy of the measured signal.
Your car’s simple-looking sensors are actually complex little pieces of hardware that are key elements in your vehicle’s electronic control network. 
