I was considering something similar for my Volvo 940 about around 2010. The idea was that I’d install a touch screen as an infotainment system where I could see stuff like OBD2 data and navigation.

While not having a functioning speedometer for a little bit (later fixed), I used my phone to see the GPS speed with the screen flipped so I could get the speed on the windshield like a HUD in some modern cars.

It annoys me that I never went through with it, because so much stuff of what I’d drawn up became standard for “fancy” cars later.