You only need one device to make and see 3D with CrossCam, but if you have two devices you can connect them using CrossCam to capture from both of them simultaneously.

CrossCam is the easiest way to make 3D pictures. The pictures you make with it are 3D just like 3D movies or VR but without any glasses or headset needed! To see the 3D, all you have to do is cross your eyes carefully and CrossCam even has a built in tutorial to teach you how to do it. CrossCam even lets you see your 3D picture before it's complete so you can tell how it will turn out in real time!