I found this open source EFIS project...

http://sourceforge.net/projects/diy-efis/

The technology is a non-starter... Windows CE.  But the concept intrigued me. So I kept digging and found:

https://play.google.com/store/apps/details?id=com.rodriguez.saul.flightgearpfdBasic

This is a more simplistic version intended to be an add-on to an open source flight simulator "Flight Gear", but the application in small experimental aircraft is obvious.

It appears all the open-source EFIS/PFD/MFD/AHRS projects went down the path of "doing it all" themselves.  That's a whole lot of propriatary work.  Small 7" tablets pack a lot usability in a cheep package most of us already own for other reasons.  The one thing a tablet can't do is collect flight data like pressure-derived airspeed, barometric altitude, compass heading, oil temperature, oil pressure and tachometer.  In short; this project is exactly what a tablet can't do. 

What if we generate AHRS + EIS airdata messages in whatever format an open-sourced-third-party display could render?  This would include attitude and SA information flat not feasible on a 16 character by 2 line ASCII LCD display in the project.   As most devices have GPS, the table interface would also include additional navigation capabilities, charts and open-source facilities databases and data logging.

Anyway, it's a really cool add on for a $50 AHRS/EIS box... Also, if you switch the processor from A ProMini to a Teensy LC or 3.1; it would be very easy to add up to 14 channels of ADC for 4-CHT/4-EGT/OT/OP/ASI/etc.  It could be a good open-source PCB project to simplify the build.