A solution for you second question could be this: You have a small weather server for your sensors. If one sensor says – hey, this plants need water. You can send a API command to start a run-once program. “Station 2 (petted plants) run 30 min” = http://yourIPorAdress:Port/cm?pw=PassMD5hash&sid=1&en=1&t=1800
Look at the API docu “under manual station run” for details.