IPhone 4

FaceTime
The iPhone 4 adds a new feature to the iPhone line, FaceTime. FaceTime allows a user to make a video call over Wi-Fi connection to another iPhone 4, fourth-generation iPod Touch, a Mac running Snow Leopard, or an iPad 2.

Camera & Photos
The iPhone 4 features two cameras, a front facing VGA camera, and a 5 megapixel rear-facing camera. The rear-facing camera can shoot video in 720p.

Retina Display
The display on the iPhone 4 is designed by Apple and manufactured by LG. It features a multi-touchscreen with pixel density of 326 pixels per inch (ppi). The screen is marketed as a "Retina Display", based that 300 ppi at 12 inches from the eye is the maximum amount of detail the human retina can process.

Death Grip
Due to the placement of the antenna in the iPhone 4, users were experiencing a loss-of-signal when gripping the iPhone 4. Apple discovered the cause of the "dramatic drop in bars" was due to the formula they used to calculate signal strength. In the update of iOS, they fixed the formula. On July 16, 2010, Steve Jobs announced Apply would provide a free case to all iPhone 4 customers to increase signal strength.

Bumper
An iPhone 4 Bumper is a ring of rubber that surrounds the edge of the iPhone 4. The Bumper is designed to strengthen the signal of the iPhone 4.

Carriers
The iPhone 4 was originally released excessively to AT&T in the U.S. On January 11, 2011, Verizon announced they will be selling a CDMA version of the iPhone 4. They have added a 'Mobile Hotspot' feature allowing users to use the iPhone as a wireless hotspot for up to 5 connected devices. They also added a new camera which they hope to solve the 'Death Grip' problem.