I think that I remember the article you mentioned in Organic Gardening magazine, because for years I wondered if I could rig up something like that for my dad who has a bad back--however he was not really all that into gardening anyway so I never did. But it was on my mind for years.
I remembered seeing a unit for sale and found it at Gardener's Supply here: http://www.gardeners.com/Standing-Garden/NewOutdoorPlanters_Cat,38-554,default,cp.html
It is a 'standing garden' with a cedar box. The serious flaw I see in this item is that it doesn't look like the legs are adjustable at all. You'd want to be able to lower it to the right height for a wheelchair, raise it up for a taller person, etc. but I think a person could design their own box with some kind of adjustable height feature.
It seems to me, though, that the 'grow boxes' made in Rubbermaid containers and set up onto a table would provide a more modular, adaptable system, easier to manage. There is plenty of info online about growing in containers, and these would be the same, just at a different height.
Other than a theoretical interest, I don't have any experience doing this so I can't really help with your questions.