I've had several requests for square image support which I'm planning to implement natively. In the meantime I've hacked up a simple utility named squareCam that will simulate a square cameraView. squareCam consist of the squareCam.js file which creates a mask that effectively squares off the classic rectangular cameraView of the ezAR VideoOverlay plugin for Cordova. You can customize the mask styling by modifying the squareCam.css file. The default mask is styled with a semitransparent diagonal hatched image (see below).
Limitations & Unknowns
I have not yet tried using squareCam with a UI frameworks such as ionic. I'll give it a try in the next few days and share my finding and any updates required for compatibility.
I've been working on some interesting computer vision experiments for performing realtime tagged and arbitrary object detection as well as simple lane and symbol detection for an automated driver. I will share more details as soon as I've advanced this work a bit further.