I've used Tetrax mounts for a couple of my phones now and they've all worked great. I would put the metal disc on the back of a case so i wouldn't have to stick anything directly on the phone. When it came to the M8 though i suspected that there would be a problem since the back of the case is where the dot view case has a magnetic switch to tell the phone when its in a dot view case.
I tested it by simply putting my phone up to the tetrax base without the disc, and the screen went off. When i powered it back on it was the dot view app so if anyone is going to use a tetrax mount, you'll have to freeze or get rid of the dot matrix app somehow. I'm rooted so i just used titanium, not sure if the app itself can be disabled on stock firmware though. After it is disabled the screen will turn off when you put it on the mount but it won't trigger dot view.