Same as a single camera... Just double.
Two SurfaceHolders, and two Camera instances.
http://developer.android.com/reference/android/hardware/Camera.html
https://stackoverflow.com/a/4591023/1602230
http://developer.sprint.com/show_thread.do?forumId=528&threadid=26999&messageId=78914
Using both cameras on android: "Fail to connect to camera service"
Refered from https://stackoverflow.com/a/8411122/1602230