Building wireless (LTE-based) sensors for most major horticultural sensing needs. Measurements include:

- CO2. Side note: I was surprised to find that most (all?) CO2 sensors used in closed plant production setups are not meant to operate below 400 ppm.

- Air temperature, pressure, relative humidity

- Photosynthetically Active Radiation (PAR)

- Addons like: wind speed, wind direction, soil moisture and Electrical Conductivity (EC)

- The coolest and most challenging: pH, EC, and flow rate

The hardest part has been running everything on battery while maintaining accuracy and using LTE (2–4G) and not common LPWAN options like LoRa. I'm primarily a software guy, so the learning curve has been huge.