Just to make sure I understand this question: are you referring to using PWS (personal weather station) as weather data source? I am not sure what you mean by “issues with APIs disappearing from the weather sites they use”. The default weather source we use is DarkSky, and we have a paid API key for it. I’ve not heard reports that the API disappears. So I assume you mean using PWS with Wunderground. Understand that currently we only support PWS through Wunderground. Whether WU API key expired in 6 months or not is beyond my knowledge — I haven’t heard of this, but if this is a new thing, I will take a look and see if there is any work-around. It’s difficult to read directly from your PWS because different PWS have completely different APIs and it’s going to be a big challenge to write code to accommodate them all. On the other hand, those that can send data to WU will all follow WU’s API standard, that’s why read their data through WU makes things much easier and streamlined.
Also, source code for all pieces of the project is available on Github. If you want to customize any part of it, such as changing the way it calculates watering percentage, change the rain delay threshold, you can feel free to do so. The github is: