Sensors in converting physical signals to electrical signals

Hi all,
Have you ever heard about sensors?
.What do you know about them? It is not too much away from you simply there are a multiple numbers of sensors in your mobile phones. They provide a multi-channel and multi-dimension connection for the digital devices.

Here are some examples for where sensors are using in hardware.

HD image processing
Audio processing
Motion detection
Environment condition detection
Geography and proximity condition detection

So sensors provide a rich interaction for the users.