Sensors used in Smart phones

Accelerometer sensor

• used to rotate the screen
  
• detect the orientation of the device and adapts the content to suit the new orientation 
• Example
• Auto-rotate pictures, videos or contents
• used in cameras for landscape mode

Proximity sensor

• detects how close the screen of the phone is to your body 
• Example
• Sense when you have brought the phone up to your ear. At that point, the display turns off in order to save battery. 
• Also stops detecting touches, as to avoid unwanted input, until you take the phone away from your ear. 
• When the phone is removed from the ear after the call, the phone resumes its previous activity.

Camera

• Clicks the photographs and sense the face or gesture
• Example
• Face recognition used for Authentication
• Eye observation using the front camera
• Gesture recognition system

Audio Sensor

• sense audio to take the commands
• Example
• SIRI is intelligent personal assistant in iphone
  (send messages, schedule meetings, place phone calls, search on internet etc.)

GPS sensor

• measures the geographical coordinates.
• Example
• Find the nearest movie, eating joint hotel, petrol pump etc.
• Navigate through voice guidance

Compass sensor

• tracks for directions
• Generally used in conjunction with your GPS sensor

Gyroscope sensor

• used to measure or maintain the orientation of a device 
• Accelerometer can only give information about linear acceleration and not orientation,
  While Gyro is combined with accelerometer, the phone can sense in all six 3D axes.

Barometer sensor

• measures pressure