I just looked them up as well. Wow, what a good idea for urban areas that get regular rainfall. From what I read (during an admittedly short amount of time), they could be adapted for small areas or large ones.
For a few moments, I considered diverting one of our rain gutter outlets to a water garden, but came back to my senses very quickly. Our rain water goes into barrels to keep the plants alive during time of no rain. Which is most of the year.