automatic watering system

Greetings fellow DIY'ers! I've just finished building an open source multi-purpose controller. Although I learned a lot, the resulting device is more proof-of-concept then finished solution. I'm in the planning stages of the next project iteration and would appreciate your feedback...

Is it true that if i put my plant's pot with drainage holes at the bottom, in a tub of water about 3 inches tall, and that it will suck up the water as needed on its own? a friend told me i could do this but i dont think it would work...if not are there any similar ways of watering a plant...