Steve wrote:
Thanks for your thoughts. Hopefully, someone from Adventure Pilot can provide a concrete answer with specific details about the hardware.
I am not an AP employee, so you may also be unsatisfied with my response, but I will try anyway.
iFly is not picky about the hardware. What it wants is data fed to it in the stream it is receiving from the ADSB-in device it is connected to. So if you can find an ADSB-in device that supports pressure altitude measurement, then iFly will probably support it.
One example would be a Stratux constructed with the optional AHRS board, which includes a barometric sensor built into it. I have this device in my plane and can confirm that iFly derives "indicated altitude" from that.
For what it's worth, it does not agree very closely to the analong altimeter in my panel, due to the various errors involved: Cabin pressure is different from static pressure outside the aircraft, the sensor is a very inexpensive part and is of unknown calibration/sensitivity, the barometric pressure reading that iFly picks up from nearby METARs for local pressure compensation may be different from the setting ATC gave me to use, etc.
Even with a "better" (even "perfectly calibrated") sensor, it will necessarily differ in reading from your panel instrument to some degree due to the other reasons listed.
In practice, I do not find iFly's indicated altitude very useful.