The iPhone 7 Plus has two rear cameras: one camera has a 28mm lens (like the iPhone 7) and a the other a 56mm telephoto lens. The housing for the two cameras is built into the alumium body of the phone.
To use Depth of Field, you select Portrait Mode in the Camera app. This engages the telephoto lens on the phone. A live preview displays what Apple's Depth of Field effect looks like before you take the photo.
The iPhone 7 Plus will not only come with new Lightning EarPods, but they will also come with a dongle (Lightning-to-3.5mm analog adapter). The dongle allows you to use headphones with an analog headphone jack.