iPhone 4

http://www.apple.com/iphone/features/home-screen.html

Multi-Touch

With its large Multi-Touch display and innovative software, iPhone lets you control everything using just your fingers. How does it work? A panel laminated on the glass senses your touch using electrical fields. It can register multiple touches at once to support advanced gestures such as pinch to zoom, two-finger tap, and more. The panel then transmits the information to the Retina display below it.

Retina Display

The 960-by-640 backlit LCD display boasts a pixel density of 326 pixels per inch, making it the highest resolution phone screen ever. To achieve this, Apple engineers developed pixels so small, a mere 78 micrometers across, that the human eye can’t distinguish individual pixels. That makes text remarkably sharp and graphics incredibly vivid. IPS technology also provides excellent color and contrast from almost any viewing angle. 

Gyro & accelerometer

iPhone 4 includes a built-in three-axis gyroscope. When paired with the accelerometer, it makes iPhone 4 capable of advanced motion sensing such as user acceleration, full 3D attitude, and rotation rate. Translation: More motion gestures and greater precision for an even better gaming experience.

Mic & Speaker

While most phones have only one microphone, iPhone 4 has two. The main mic, located on the bottom next to the dock connector, is for phone calls, voice commands, and memos. The second mic, built into the top near the headphone jack, is for FaceTime calls and for making your phone calls better. It works with the main mic to suppress unwanted and distracting background sounds, such as music and loud conversations. This dual- mic noise suppression

helps make every conversation a quiet one.