I try never to sit at airports, particularly at the gate while waiting for a flight. If you're going to be inside an airplane and sitting on your ass for the next several hours, I think you should try to keep your feet as much as possible beforehand.
However, I'm able-bodied. For those with back or leg issues, frequent sitting could be a godsend, particularly in locations where there are no seats available. So I think that this wearable LEX Bionic Chair, as crazy as it looks, could be extremely useful to a subset of the population:
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The LEX weighs a little over two pounds, yet will support more than 260 pounds. They're going on Kickstarter for $245 a pop, and it's already been successfully funded, with 22 days left at press time.