I recently came upon this trail chair from REI (http://www.rei.com/product/765286). Thought I share as it works really well for me. It provides some cushioning, good insulation against cold and moisture and great back support if you're sitting somewhere for long time. If unbuckled it also acts as a mat to lie down on for the really low-angle shots.
The only disadvantage is that it doesn't roll up like a yoga mat and is therefore not very compact to transport. But that is easily overcome by the back support in the chair configuration.
JR I've been using the Walkstool, I clip it to my belt and carry it that way. When you pull the legs out its 26" and with the legs in its around 18. heres a link Rod http://www.bhphotovideo.com/c/produc...e_Folding.html