I ordered a DodoCase version and it arrived today. I wasn't sure how it would work with my Note 3, but it works pretty well. The screen is almost exactly the size of the opening and so gives more viewing screen than smaller phones would.
I made three minor modifications to it. One was a cutout on the top to allow me to access the power button. Another, similar cutout (this time I only cut three sides and secured it loosely with tape) to relieve the pressure on the volume button and allow me to change the volume. The third was a minor enlargement of the camera hole to allow the camera lens full access. All three cuts are about 1/4 inch deep and the width of the needed buttons/camera, very minor, and very effective.
I haven't had a LOT of time to play with it yet, but it works very well. I look forward to comparing it to my wife's S5 when she gets home.
Oh, I had some double sided velcro around and found that strip of that will hold it to my head quite well too. So far I haven't decided how to attach the velcro, but it works just wrapped around the cardboard and my head.
All things considered, I am very pleased with the way it works with my Note 3!