As grissankara said, use EasyAR 3.1.0 insteady 3.0.1. See this guide to configure easyAR3.1.0.
After that, you need to download the samples. Then, open:
Assets -> Samples -> Scenes -> DeviceSupport -> Camera_VideoCamera.unity.
Find "VideoCameraDevice" prefab in the scene and you will see VideoCameraDevice.cs script.
Inside this script you will have functions like:
Open(); Close(); ...
Call this function to open or close the camera. See the VideoCameraSample.cs to understand more.
If you need more help, tell me.
Have fun! Hehe