If you are designing your own intelligent “Graden Computer” with an optional digital plant moisture sensor/water pump controller that lights an LED to alert the user when it is time to water a potted ...

This Arduino-powered Shiftbrite ... He even provides the wiring diagram for his controller and the config file for his lights. If you have the time and are the DIY type, you could follow his ...

Here is the diagram of my Arduino infrared close proximity sensor. As you can see, the core part of my experimental setup is an Arduino UNO, but other compatible microcontrollers can also be employed.