A few days ago I finally received a response back from the makers of Dario! While it did take 14 days to hear back, I'm glad they responded.
It seems like, based on their email, that the Nexus 6p will not be supported in their future updates. While this is disappointing, it isn't all that surprising. Looking at their USA/International site, it shows only photos of iPhones, and only lists iPhones under their models (screenshot here from http://mydario.com/the-app/). Although they said they would be "[updating their] list of supported phones for the Samsung and LG families," updating could mean removing entirely instead of adding new models.
I guess my next step is to take them up on their offer the speak to their professional support services to see if I can get a refund.
You can read their full response below:
Thank you for taking the time to give us your feedback. It is important to hear back from our users and to understand the needs of our customers.
In our next app upgrade, which is currently being verified for release, we will update our list of supported phones for the Samsung and LG families.
We would like to make the Dario Smart Glucose Meter system as widely available as possible, but we also want to ensure that we can responsibility validate all the phone models that we proclaim to support. Please take into consideration that there can be a great variance between the hardware of each Android phone and how it interacts with our meter and app. Our device was tested and approved by the relevant regulatory authorities. The device accuracy meets all standards. The inaccuracy, presented in the movie posted in your blog is related to the unsupported phone that was not verified. We advise potential and current users to review the list of supported smartphone devices as stated on our packaging and website.
Dario understands and takes very seriously the need for our users to have a glucose meter that they can rely on when using it with one of our supported phone models. We are continuing to upgrade our app and have team members who are dedicated to developing and maintaining the Android version of the app.
We are welcome you to contact our professional support services for any needed assistance or refund request.