Realdash looks good,
I've been using this on my dash, in front of the 406 coupe instrument panel, fits well using the iPad mini (although this pic is not of the ipad mini):
With the the Supercars Speedometers app (handy MPH, as my car is in Kmh imported from Ireland, and not accurate anyway because of 19" wheels, also found the visual and sound alarm for over a preset speed limit useful). Only issue is it obscures the fuel and temp gauges.
It would be rather brilliant to have data on temp and fuel feeding into an app like Realdash, so I'm keen tyo see how you get on.