Overlay a live WiFi camera image
great, I got it . This is easy and possible, SO first of all i need to know the camera you are using to record or live preview your work ?

You need a good high resolution camera , which can zoom at that detail what was shown in your Youtube link . 
Secondly if the camera has live streaming / mirro link options that will be cool , cause you can connect to TV  / Mobile in android and get the camera  live streaming in you mobile or tablet. 
Your tablet with android 6.0 is good enough . 
The important thing is you Camera that will record / live stream when you work. 

Secondly , you can do this wirelessly and wired way. 
Wireless ,if you cam has a wifi direct / mirrocast , airplay like features , wired with it supports direct camera raw data to pc streaming ...

Hope this helps..