Keeping Window Boxes Watered

I have a problem remembering to water my three window boxes. An idea I got recently from the book You Grow Girl is to take plastic bottles, I used plastic tonic water bottles, cut a few holes in the lid and then cut the bottom of the bottle off. You then dig a hole near the plants and shove the bottle, lid down, into the soil. The water drips continuously preventing your plants from drying out-death and you just add more water to the bottle as it empties. This is a mini irrigation system and it has worked wonderfully for me!