I live in an apartment that doesn't have a garden, but I do have a small roof outside my bedroom and I wanted to start a vegetable container garden on it. The idea of self watering containers appealed to me, but even with self watering containers I would still have to crawl out my bedroom window with multiple buckets of water every few days to keep the containers full.
What I needed was a way to keep multiple containers watered from a central reservoir that was easily accessible. I couldn't just connect the feed tubes straight from the containers to the reservoir because then it would just empty out, unevenly watering the containers and over watering the plants. However I didn't want wires hanging out my window, so I didn't want something that required electricity. It also had to be simple, so it could run with no need to dig it up and fix it, and it had to be cheap (or free), so I could repeat it on multiple containers and expand my garden without spending a lot of money.
The containers I've designed use the same self watering system as the earthbox concept, but I added an automatic shut-off valve to each container so that multiple containers can be gravity fed from the same reservoir. Each container regulates how much water it takes from the reservoir so, however many containers you have in your garden, all you have to do to keep them all watered is to make sure the reservoir stays full, no need for electricity, pumps or timers.
Construction is fairly simple and all parts are readily available for very cheap (almost all are very common and could be found for free if you are so inclined).
If you do decide to buy all the parts, it will set you back about $10-$12 per container