I have been very happy with my personal Weather Underground Personal Weather Station, a $149 Ambient 1400 http://www.amazon.com/Ambient-Weather-WS-1400-IP-Observer-Monitoring/dp/B00O9YIEJW It took me about an hour to install it and have it visible online, and gives me temperature, wind speed and direction, rainfall rates and totals, atmospheric pressure, solar radiation, and UV radiation. It is particularly interesting to watch the rainfall rate and observe the runoff conditions. 1″ of rain over a week is much different than 1″ in an afternoon.
It would be cool to allow customization of OS capabilities around an on-site PWS. We could use a full Evaporative Transporation ETo model such as is used by the industry. (I find the current Zimmerman model to be so far out of line from my real needs as to be unusable). It would be nice to allow microclimate adjustments to the OS zone control (slope and soil conditions for run off, seasonal differences in sun angles, tree foliage, shadows, etc.). I wouldn’t expect the main code to do all of this, just give us the hooks for a plug (preferably Python) that we could access this at a more granular level.