You'll of course need a backdrop too, but the reflective gray one they sell is a lot more flexible (and works in a variety of conditions). The LED ring itself is placed right around the front of your lens and shines either blue or green light towards your subject, reflecting off gray fabric background called Chromatte (you'll have to buy that too). According to Reflecmedia the resulting key is clean and has a number of advantages compared to traditional green screening, which requires a more carefully conditioned surface and can result in spill on the subject. You can purchase the kit for $1900 and there are a whole lot of different bundles available as well.
More of No Film School's coverage from the NAB showroom floor: