Ok so it might not sound *terribly* relevant when it comes to cacti. Nevertheless, does anyone know of an good automatic watering systems?

I'm thinking along the lines of either self-watering pots or DIY "home" sprinkler systems.

Self watering pots are a good idea if you are trying to grow water-thirsty plants in a dry environment. Basically, all they do is trap the water which is already in the pot. I've used them with some success for non-succulent plants. However, I've never tried them with cacti or succulents because generally such plants *need* the drainage, and if their roots get wet then rot may well set in.

That said, I can definitely see the use of such pots for growing pereskiopsis.