Couple of things from a nerd a pilot/owner of a certified aircraft:
1. Look in the relatively new
FAA NORSEE policy, which might allow you sell some of these units into the certified market as well, as "Non Required Safety Enhancing Equipment".
Some feature considerations to make it appeal to the widest audience:
2. To facilitate installation in 6-cylinder turbo aircraft, add another K-type channel for turbine inlet temperature and code to treat that as "first-class citizen". (There are some twin-turbo aircraft with two TIT channels needed as well if you have enough ADCs or add an analog switch or additional ADCs.)
3. To facilitate installation in inter-cooled aircraft, add another (likely K-type) air temp sensor, such that a user could use the carb temp channel and this new temp sensor to have all of OAT, CDT, IAT and calculate intercooler efficiency numbers to track intercooler cleaning requirements.
4. Consider a caution and warning light output. Some users may want a CHT caution at say 390°F but a CHT warning at 420°F.
5. The "onboard memory" is ambiguous on the github page. I want at least 2 second (ideally 1 second) logging of datastreams for at least 25 flight hours (more if it's hard to download the data).
6. Make it clear that downloading datalogs is possible.
7. It's unclear whether you have fuel totalizer functionality (ded reckoning of fuel onboard), but that's extremely handy (and, on balance, safety enhancing by a significant margin).
8. Consider adding RS-232 or ARINC429 input channel to take inputs from a serial connected GPS unit (dist and time to next waypoint, dist and time to end of flight plan, current lat, long, alt). The first two are for fuel totalizer usage and the last three for data logging.
9. You might be able to get by with one fewer button using a short press to advance and a long press for previous. This is fairly standard and might be easier to use in turbulence than buttons that are too close together.