This is one those things that seems really cool on principle, but doesn't quite pan out in practice. The Aqua Plant is another consumer curiosity we picked up in one of Tokyo's labyrinthine subterranean malls. It's a glass bulb with a narrow pipette that you fill with water and stick in your plant's soil, ostensibly providing a steady stream of water as the soil needs it.
As plant adornment, it's kinda neat. As a practical substitute for watering, not so much. Our first concern was root rot, but we needn't have worried. Root rot would require getting water into the bulb in the first place, a challenge given the narrowness of the pipette, which was also too long to submerge readily.