How can you see a picture of a remote quadrocopter from the iPhone screen?

Question

Quadcopter

It's a very dumb question, but it's there.
https://youtu.be/J2i8my9_hlI?t=4m44s (time 4:44) using iPhones to watch the picture from the cameras on the quadcopter.
How does this picture get on the smartphone screen? Direct Wi-Fi channel from the quadcopter or via wiring from the "remote control" that steers the quadcopter? In that case, what is this interface?

Answer 1

Through WiFi.
Such things are indicated in the specifications of the model (or accessories).
For example