Scan Guage II with blend mount
I have a Scan Guage II with a blend mount to mount the unit above the mirror - this thing is great, displays almost any parameter you could want, plugs into OBDII port. Manuals included, only used for a few months in my 14 GT - I am not running this in my 15, with all the other info the new car shows it would be redundant, butcon a bird they are great - I have owned three of these so far, I really like them.
Here's the actual unit for sale in my 14 GT
Here's the one I had before this one, in my old F150, using the same type of blend mount
Here's the same unit that ended up in the F150, in my old 13 mustang
And here's how I mounted one in my 95 bird way back in 2008-2009
2015 Mustang GT Premium / Manual / 3.55 / Recaro