http://www.ergotron.com/Products/Des...S/default.aspx

I used two of these particular arms mounted on the edge of a table, and sat the lcd over a Laz-e-boy chair. They worked great, had just enough tension to stay in place and could swing up, down, in, and out, all day. After using these I would say it the tension could be set just right to allow writing on a tablet. All you would need is some kind of sturdy post and three inches of edge to mount it on. I wouldn't count on these lasting 10 years under heavy use, but the medical quality ones should if durability is a concern.