Ahh, I wouldn't say I am so much advanced, a SCWD is a simple device it's been around for a year or more I think... it has one inlet, two outlets, pressure builds up inside, and switches flow from A outlet to B outlet, timing depends on the strength of the pump driving it. this produces a wave action that is beneficial to corals and anemones. Also makes a nice vigorous current for your fish to navigate.
Refugiums are the next generation of the SUMP, which I am sure you are familiary with. Sumps were created to take the equipment out of the tank, your drain water out of the tank, filter it, heat it, skim it, run through a calcium reactor, you name it, and then use a pump to send it back up into the tank. The refugium is taking this method, and returning to a naturalistic approach. (as far as you want to go.) you add lights to the setup as if it were a main tank, your skimmer and other equipment can still run off of it, but in addition, now you add a THICK live sand substrate, and organisms that will keep it stirred up. Live rock and macro algae are also used here, liverock being the best Bio filter ever imagined, and macro algae can be A) harvested and traded/destroyed, or fed back to your herbivores. Some people have gone completely away from the technology, removing protien skimmers and all filtration, and just use powerheads to circulate the water. THey grow mangroves out of their refugiums, that suck up the nutrients in the water.
In addition, regugiums provide a nice breeding place for amphipods and copepods, these little critters, free from predation in the main tank, reproduce, and get sucked into the return and deposited in the main tank, where fish, anemones, feather dusters and corals eatem up.
I love the bio-diversity capable of being achieved in a reef system. It is quite simply, awesome.