The monitoring system I use for my mini hydroponic garden. As of now, the system uses temperature, humidity, light, and water level sensors, however more sensors like pH could easily be added.
The raw values are read from the sensors connected to the Arduino. It is connected to a Raspberry PI which constantly reads values over a usb bus to the Arduino.
The reason for a PI is that we can use it as a server for a database, but also it has public network access and can post to our database if it's not located on the PI. One could use a WIFI-shield on the arduino and not use the PI at all.
The PI posts the values it reads over the usb cable to the server via a python script which runs at all times.
