Last few days I continued to tweak the hardware. I decided to remove the lightning sensor since it was: a) discontinued, b) of questionable performance. While the idea was interesting, I really don't want to add such a complex circuit which may require careful antenna tuneing and even still, from what I've read in different places, I'm not sure if the reported range and detection performance is real.
On the other hand I decided to add a small EEPROM memory (maybe around 16KB, but can be modified later easily) to hold user settings. I originally considered storing this in the on-board flash (given there's enough space left), but that would require erasing whole pages just to change one setting which would really wear it unnecessarily. I believe an EEPROM, which can erase in smaller blocks and is much longer lasting, is more suitable for this. I'm not sure yet if storing daily data (or even long term data) such as temperature, altitude variations over time, and so on, is feasible.
Lastly, I'm considering changing the IMU, which currently is 6-axis (magnetometer + accelerometer, and some weird gyro emulation from that) to a 9-axis (the LSM9DS1). While it is three times more expensive, it is incredibly low-power and would even allow for continuous measurement without wasting much battery (I'm talking about a few uA while producing readings at 10Hz). Anyway, as this would be the second time I change the IMU so I will wait a bit on this change. Downside is this is a LGA24 package which does not even expose pads to the side so it will be quite a challenge to solder it using the hot-air gun.
I realized that one major hurdle in making real-progress with this project is the fact that I don't really know when I could send this for fabrication and to buy the required components. The reason for this is that currently it is difficult for me to justify these expenses, considering current economic situation. While it not may sound much, in my country the USD exchange rate is really high compared to wages and import taxes are also in general high (I even need to resort to FedEx to even ensure the packages arrives).
So, if you're interested in this project and would like to see it moving, I would really appreciate if you could donate on my kofi page. I will soon update it to set a goal with my estimate for PCB build and components. In the mean time, here's the link: