Gents:  Just saw this in "Sport Aviation."  I have two Cheltons and a backup 
steam ADI.  Seems this little unit gives Airspeed and Heading and Altitude and 
VS, as well as attitude.
 
 Any reason to not replace my single purpose steam attitude indicator with 
something like this for a thousand bucks?
 

John,
I have a Dynon D-10A mini-EFIS in my IV-P and it’s been absolutely reliable for 3+ years and 750+ hours. I have never seen it fail to erect, and it’s never blanked or tumbled as far as I know. Costs just a bit more than the TruTrack unit you reference, but it’s a true ADI. I believe the TruTrack unit is basically a turn indicator with a modified display?? I think both the Dynon and the TruTrack units require electrical power to operate, and depend on solid state measurement/sensing devices that are sensitive to electrical system issues; and especially lightning. 

I have a 2-screen Chelton Sport as my primary EFIS, and had intended to use the Dynon as my backup instrument, but older and wiser folks convinced me (literally at the last possible time when I was building my panel) to add mechanical ADI, altimeter and airspeed. I can honestly report that I’ve never been solely dependent on the mechanical gauges while flying the airplane, but in two instances when the Chelton’s blanked/reset (once on an ILS), it was most reassuring to look over and see the steam gauges and the Dynon in complete agreement as the Cheltons automatically reset and returned to the fold.

I believe the day will come when we won’t have mechanical gauges as an alternative, but we’ll have several more years of experience, lessons learned, and improved electronic instrumentation by then. For my 2 cents, the urging of two good friends to install backup mechanical instruments was some of the best advice I received during building.  It ranks above similar recommendations to install an aircraft engine, rather than my truly home-built Chevy V-8! In hindsight, both were the right decisions—for me.

Bob