The final cut of the 9th episode of the Tesla Motors Club Podcast, featuring Chad Schwitters, the former president of Plug In America, is now available. You can watch it now on YouTube or listen to it on all major podcast networks.
I do like your apps and solution and before I took delivery of my car I would have been very happy to see this. I may still try what you have done but after having driven the car for about 1300 miles I think I'm OK with the screen speedometer. Thanks for the idea however and I'm sure many will find what you have come up with great. This forum is a nice place to show these sort of solutions.
How much of a variance do you notice between what the car is reporting and the two apps? I would imagine the two apps are reporting the exact same thing as each other since they are most likely taking telemetry from iOS.
They were usually very close. I am not so sure that the car is using GPS. It may have speed sensors taking direct readings so (for instance) it could continue to show speed in a tunnel.
Note, I stopped using the phone on dash and dashboard app. I would get too many distracting reflections in the windshield and I decided I was better off with an uncluttered dash with better visibility.