Aqua Globes for the ferns that we keep on our front porch. We were going on a trip of some sort and I was afraid they were going to dry out totally, so this seemed like a short-term solution. They worked, in that they kept the ferns from totally dying.
After the ferns came down, these globes came inside. I've since plugged them into the pots of our Asparagus Ferns to keep them alive during these dry winter months. So far, so good. They drip out water in very small quantities, so I'm not sure they're adequate as the sole watering mechanism, but as a supplemental technique, I'd recommend them. You'll still have to water your plants every once in a while, but these globes will make that job less of a hard requirement.