Ohh yes that door is good!
As I was watching the video I was trying to think of how the piston could be used to make a lift. Perhaps some sequence of pistons lifting a stone platform? Hmmmm....
What happens when you activate several pistons stacked on top of each other? You could bury the retracted versions so that the top one appears at ground level, then when you expand them all at once (or sequentially) the new top would be at twice the height.
EDITED: 24 Jun 2011 17:08 by CAER