Hello all, I just read through the posts here and wanted to share my experiences so far with Mirrorlink and my HTC One M8. My setup is a little different. I actually have an AT&T phone that is just a little over a month old.
A couple of weeks ago, I bought a new 2014 Honda Civic EX that has the Display Audio unit in it. At the time, I had no expectations of it working with my phone at all. I did read that the Display Audio unit had some support for the iPhone. As I researched that a bit, I was really interested in the features that it added. So, I started to look to see if there was any support or plans to support Android. Everything that I read said that Honda would not be doing anything for the 2014 model to support android. That was a bit frustrating because I don't plan to buy another new car for a long time and the features looked really useful. I did see that it supported "Mirrorlink" though.
Out of curiosity, I plugged by phone into the USB port in the car, and a new "app" was available in the Display Audio unit. It was simply called "Car" and had a steering wheel icon. I selected that and it started the HTC Car app on my phone and replicated it to my screen! Fantastic!
When I put the car into drive, most of the apps available within the HTC Car app would disable. I think the only things that remained enabled was Navigation and Music. My sound worked, but would get choppy at times. That was annoying, but not really a problem because of the features that it added.
Last week, AT&T had a new OTA update available and I proceeded to install it. It updated to 4.4.3 android (instead of 4.4.2) and it also updated HTC SDK API from 6.17 to 6.25. The next time I plugged my phone into the car, there were a couple more apps available - Car, Speak, and Music. This was very cool until I put my car into drive. Now, the HTC Car app would become disabled as soon as I was in drive. This meant that ALL replication to the screen would be replaced with a message saying "For safety purposes, this application is not available while driving".
I've spent the time since then trying to learn more about mirrorlink, HTC and Android. I unlocked my phone, rooted it and made it S-OFF. Unlocking my phone basically disabled Mirrorlink. While my phone was unlocked, no apps would be available and I would instead get a message saying: Smartphone not compatible.
Yesterday, I downgraded to the software version that I had prior to the OTA update. I then relocked my bootloader and all is now working how it was. I did discover that the phone needed to be setup with Bluetooth for the Mirrorlink connection to work even though all sound and screen replication seems to be using the USB port.
It really looks to me like HTC has screwed up the Mirrorlink implementation in the 6.25 version of Sense. I'm not sure what version of Sense that Verizon M8's use, but it is worth looking at.