I used this phone holder: https://www.amazon.com/gp/product/B01N210GDQ/ But had to modify it... Cut the left edge so the camera can see forward. I tried a bunch of Speedometer and Dashcam apps, and currently like "GPS Dash" & "CarCameraDVR"
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.
I want oil pressure and temperature, coolant temperature, volts, amps, tachometer, turbo boost and vacuum all displayed!
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.